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Old 12-16-2005, 13:01   #1 (permalink)
alan4spamoffd@tpg.com.au
Guest
 
Posts: n/a
XJ40 Bulb failure messages (undbelievably another thread!)

Morning all, from Stinking Hot Australia! (not that I'm complaining)

Bulb failure messages! There have been so many threads about this or
containing this and other stuff. I have such a problem and thought it
might be useful to bring the info to date together once more and seek
further info. Apologies if this is old hat to some; it may hep others.

An important point to realise is that the bulb failure system on an XJ40
is very sophisticated. The condition of all the external bulbs is
monitored *even when they are not on!* This is achieved by a group of
computerised modules (someone described them as "one at each corner of
the car") keeping an eye on the resistance of the bulb circuits using a
very low current (and thus voltage, not on as in 12 V). Any failed bulb
or circuit will not give a reading within the limits and the failure
module signals a fault, even when "off". Of course, the iginition has
to be on in order for the whole system to be energised.

The small current used in this test is intentionally low enough for eg
corroded bulb contacts or even out of spec globes to give the failure
signal. Dry joints in the BFM modules themselves can do the same
thing. The most common cause is likely to be an actual bulb failure,
perhaps a side repeater, one of the number plate lamps, or a bulb
overlooked in checking, such as the boot lighting.

So, the first thing is the check every external bulb (including reverse
lamps, blinkers and brake lamps) and the boot lighting, that each globe
is OK, and then clean its contacts and the receptacle contacts. Note
that this must include the fog lamps on the rear. If they are not
fitted to the front then dummy resistors are fitted in blank plugs. My
plugs/sockets are yellow and contain normal 1 K 1/8 watt resistors (one
to each side). Readings of 1K plus or minus 10% are OK - it's not that
critical because bulb filaments are not dead accurate anyway - hence the
reasonable tolerance.

I suggest all these things first, because working on the BFM modules
involves a little awkward dismantling and then a sure hand with a fine
soldering iron. The modules are labelled "Bulb Relay Module" or
suchike. They are a slab shape smaller than a paperback book and in the
rear they are bolted to the interior edges of the boot, behind the bulb
modules and behind the carpet. One screw off the carpet and pull
forward to reveal the module. After unplugging and removing the module,
straighten the tabs on the soft aluminium cover and prise off. A
printed circuit board bearing relays and other components will be
revealled. This board is notorious for "dry" joints. If you are not
sure what a dry joint is, then you may be doing the wrong job yourself!
Any competent electronics enthusiast or technician should be able to
help. Anyway, reflow suspect joints using a fine soldering iron. I
think a check of the diodes with an ohm-meter is in order at this
stage. They can be tested in circuit. Should be a low resistance one
way - very high (or infinity) the other. They are apparently 1N4007 or
similar. Very cheap. In an average of 50% of cases this will clear the
trouble. Or else move on to the front modules. They are similar in
shape and mounted just above and behind the headlamps. Removal is much
more fiddly. Disconnect battery negative (after being sure you have any
re-activation codes for the audio!). For the right hand side, unbolt
and push aside the extrenal relay bank (A/C etc). The bulb relay module
is connected by two easy to remove (one black one yellow) connectors,
plus a connector to the rear of the headlamp (fiddly to put back - just
pull off to remove). One more connection and that is a black wire to
the earth, bolted to the frame. It's quite fiddly to get to that and
handy to have a magnetic pickup tool to retrieve it when you drop it!
Note that there are other connecting tags to that bolt. Should now be
able to unbolt and remove the bulb relay (failure) module. Removal of
the cover is as before. You will find that inside there is again a
printed circuit board, but also another mounted to the top as well.
This can be prised off and all contacts on both boards checked for dry
joints and once again diodes as well. Replace cover and press in tabs
slightly as before. Re-attach the earth wire (*very* important and very
fiddly), the headlamp connector (very fiddly - have to work by feel),
and then reattach the two connectors. It's so fiddly that I think it is
worth checking after doing one, in case that clears it.

Apparently, the vast majority of bfm faults will be cleared by one of
the above. Well, here's the rub. I've done all these things and
*still* I have the rogue warning signal! So, in case you were thinking
"he's obviously an expert" by now, you can see that I'm obviously not!
I would appreciate any input beyond the above!

Hope the above will help some... and that someone will help me!

Regards to all
Alan



  Reply With Quote
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Old 12-16-2005, 19:02   #2 (permalink)
WayneC
Guest
 
Posts: n/a
Re: XJ40 Bulb failure messages (undbelievably another thread!)

Too bad that "very sophisticated" US $2K+ bulb failure system isn't even
smart enough to point at the problem lamp! Seems to me like it's
actually pretty danged stupid, considering it's price. Even the old
American cars of the fifties were smarter: if your dash lights went out
and the fuse was OK, you pretty much knew a tail light was burnt out. If
a front turn signal light went out, well, hopefully you don't turn in
front of oncoming traffic so close up that they'll crash into you if
they don't see your signal and jam on their brakes! On the Jag, you not
only don't know what went out, front, rear, or side, but you have to
trouble-shoot and second-guess the failure monitoring system too!

When do you get the failure warning on your car? Mine (89 XJ40) is
random, but mostly associated with applying the brakes and/or the left
turn signal... I'll get one normal turn signal cycle (2 clicks) and then
the clicking speed doubles (which is the normal audible part of the
failure alert) and the dash warning appears, and often the turn signals
also stop blinking at that point (but not always). It does not happen
every time I use the left turn signal.

As I previously stated on another thread, I have done pretty much
everything suggested, more than once. That includes renewing all the
rear bulbs except for license bulbs, cleaning the bulb sockets,
resoldering all the joints in the rear BFM's, swapping the rear BFM's
side-to-side, and replacing the left rear BFM with a used BFM.

All my lights are operable (ie, no burnt bulbs), except the left rear
turn signal sometimes stops operating (both bulbs) when I have this
failure warning (sometimes it doesn't, but the error warning still shows
on the dash and the click speed doubles). I haven't changed the front
turn signal bulbs because the turn signals don't neccessarily need to be
on when I get the problem (it can happen with the brake lights on), so I
assume it's associated with the rear; but, I have had the warning pop on
when I'm simply cruising steady-state on the freeway (rarely, but it HAS
happened), therefore I intend to change out the front turn signal bulbs too.


alan4spamoffd@tpg.com.au wrote:
> Morning all, from Stinking Hot Australia! (not that I'm complaining)
>
> Bulb failure messages! There have been so many threads about this or
> containing this and other stuff. I have such a problem and thought it
> might be useful to bring the info to date together once more and seek
> further info. Apologies if this is old hat to some; it may hep others.
>
> An important point to realise is that the bulb failure system on an XJ40
> is very sophisticated. The condition of all the external bulbs is
> monitored *even when they are not on!* This is achieved by a group of
> computerised modules (someone described them as "one at each corner of
> the car") keeping an eye on the resistance of the bulb circuits using a
> very low current (and thus voltage, not on as in 12 V). Any failed bulb
> or circuit will not give a reading within the limits and the failure
> module signals a fault, even when "off". Of course, the iginition has
> to be on in order for the whole system to be energised.
>
> The small current used in this test is intentionally low enough for eg
> corroded bulb contacts or even out of spec globes to give the failure
> signal. Dry joints in the BFM modules themselves can do the same
> thing. The most common cause is likely to be an actual bulb failure,
> perhaps a side repeater, one of the number plate lamps, or a bulb
> overlooked in checking, such as the boot lighting.
>
> So, the first thing is the check every external bulb (including reverse
> lamps, blinkers and brake lamps) and the boot lighting, that each globe
> is OK, and then clean its contacts and the receptacle contacts. Note
> that this must include the fog lamps on the rear. If they are not
> fitted to the front then dummy resistors are fitted in blank plugs. My
> plugs/sockets are yellow and contain normal 1 K 1/8 watt resistors (one
> to each side). Readings of 1K plus or minus 10% are OK - it's not that
> critical because bulb filaments are not dead accurate anyway - hence the
> reasonable tolerance.
>
> I suggest all these things first, because working on the BFM modules
> involves a little awkward dismantling and then a sure hand with a fine
> soldering iron. The modules are labelled "Bulb Relay Module" or
> suchike. They are a slab shape smaller than a paperback book and in the
> rear they are bolted to the interior edges of the boot, behind the bulb
> modules and behind the carpet. One screw off the carpet and pull
> forward to reveal the module. After unplugging and removing the module,
> straighten the tabs on the soft aluminium cover and prise off. A
> printed circuit board bearing relays and other components will be
> revealled. This board is notorious for "dry" joints. If you are not
> sure what a dry joint is, then you may be doing the wrong job yourself!
> Any competent electronics enthusiast or technician should be able to
> help. Anyway, reflow suspect joints using a fine soldering iron. I
> think a check of the diodes with an ohm-meter is in order at this
> stage. They can be tested in circuit. Should be a low resistance one
> way - very high (or infinity) the other. They are apparently 1N4007 or
> similar. Very cheap. In an average of 50% of cases this will clear the
> trouble. Or else move on to the front modules. They are similar in
> shape and mounted just above and behind the headlamps. Removal is much
> more fiddly. Disconnect battery negative (after being sure you have any
> re-activation codes for the audio!). For the right hand side, unbolt
> and push aside the extrenal relay bank (A/C etc). The bulb relay module
> is connected by two easy to remove (one black one yellow) connectors,
> plus a connector to the rear of the headlamp (fiddly to put back - just
> pull off to remove). One more connection and that is a black wire to
> the earth, bolted to the frame. It's quite fiddly to get to that and
> handy to have a magnetic pickup tool to retrieve it when you drop it!
> Note that there are other connecting tags to that bolt. Should now be
> able to unbolt and remove the bulb relay (failure) module. Removal of
> the cover is as before. You will find that inside there is again a
> printed circuit board, but also another mounted to the top as well.
> This can be prised off and all contacts on both boards checked for dry
> joints and once again diodes as well. Replace cover and press in tabs
> slightly as before. Re-attach the earth wire (*very* important and very
> fiddly), the headlamp connector (very fiddly - have to work by feel),
> and then reattach the two connectors. It's so fiddly that I think it is
> worth checking after doing one, in case that clears it.
>
> Apparently, the vast majority of bfm faults will be cleared by one of
> the above. Well, here's the rub. I've done all these things and
> *still* I have the rogue warning signal! So, in case you were thinking
> "he's obviously an expert" by now, you can see that I'm obviously not!
> I would appreciate any input beyond the above!
>
> Hope the above will help some... and that someone will help me!
>
> Regards to all
> Alan
>
>
>

  Reply With Quote
Old 12-16-2005, 21:01   #3 (permalink)
Don Young
Guest
 
Posts: n/a
Re: XJ40 Bulb failure messages (undbelievably another thread!)

A technique I have found useful in troubleshooting intermittent faults is to
isolate each wire and check its continuity under a fairly heavy load. Such a
load can be a turn or stop lamp fed by 12 volts. This will nearly always
find any loose, corroded, or otherwise poor connections. I found a badly
corroded wire under the floor carpet by this method. Be sure to disconnect
anything else from the wire under test and be alert for signs of overheating
if the lamp does not burn or flickers. Some very obscure problems can be due
to poor contacts in plugs and sockets. Sometimes the socket contacts will be
slightly spread. You can measure the pin and use a wire or drill bit of the
same or slightly smaller size to check the tension of the sockets.
Don Young
"WayneC" <WayneC@linkline.moc> wrote in message
news:11q6ovupdbd5r8a@corp.supernews.com...
> Too bad that "very sophisticated" US $2K+ bulb failure system isn't even
> smart enough to point at the problem lamp! Seems to me like it's actually
> pretty danged stupid, considering it's price. Even the old American cars
> of the fifties were smarter: if your dash lights went out and the fuse was
> OK, you pretty much knew a tail light was burnt out. If a front turn
> signal light went out, well, hopefully you don't turn in front of oncoming
> traffic so close up that they'll crash into you if they don't see your
> signal and jam on their brakes! On the Jag, you not only don't know what
> went out, front, rear, or side, but you have to trouble-shoot and
> second-guess the failure monitoring system too!
>
> When do you get the failure warning on your car? Mine (89 XJ40) is random,
> but mostly associated with applying the brakes and/or the left turn
> signal... I'll get one normal turn signal cycle (2 clicks) and then the
> clicking speed doubles (which is the normal audible part of the failure
> alert) and the dash warning appears, and often the turn signals also stop
> blinking at that point (but not always). It does not happen every time I
> use the left turn signal.
>
> As I previously stated on another thread, I have done pretty much
> everything suggested, more than once. That includes renewing all the rear
> bulbs except for license bulbs, cleaning the bulb sockets, resoldering all
> the joints in the rear BFM's, swapping the rear BFM's side-to-side, and
> replacing the left rear BFM with a used BFM.
>
> All my lights are operable (ie, no burnt bulbs), except the left rear turn
> signal sometimes stops operating (both bulbs) when I have this failure
> warning (sometimes it doesn't, but the error warning still shows on the
> dash and the click speed doubles). I haven't changed the front turn signal
> bulbs because the turn signals don't neccessarily need to be on when I get
> the problem (it can happen with the brake lights on), so I assume it's
> associated with the rear; but, I have had the warning pop on when I'm
> simply cruising steady-state on the freeway (rarely, but it HAS happened),
> therefore I intend to change out the front turn signal bulbs too.
>
>
> alan4spamoffd@tpg.com.au wrote:
>> Morning all, from Stinking Hot Australia! (not that I'm complaining)
>>
>> Bulb failure messages! There have been so many threads about this or
>> containing this and other stuff. I have such a problem and thought it
>> might be useful to bring the info to date together once more and seek
>> further info. Apologies if this is old hat to some; it may hep others.
>>
>> An important point to realise is that the bulb failure system on an XJ40
>> is very sophisticated. The condition of all the external bulbs is
>> monitored *even when they are not on!* This is achieved by a group of
>> computerised modules (someone described them as "one at each corner of
>> the car") keeping an eye on the resistance of the bulb circuits using a
>> very low current (and thus voltage, not on as in 12 V). Any failed bulb
>> or circuit will not give a reading within the limits and the failure
>> module signals a fault, even when "off". Of course, the iginition has
>> to be on in order for the whole system to be energised.
>>
>> The small current used in this test is intentionally low enough for eg
>> corroded bulb contacts or even out of spec globes to give the failure
>> signal. Dry joints in the BFM modules themselves can do the same
>> thing. The most common cause is likely to be an actual bulb failure,
>> perhaps a side repeater, one of the number plate lamps, or a bulb
>> overlooked in checking, such as the boot lighting.
>>
>> So, the first thing is the check every external bulb (including reverse
>> lamps, blinkers and brake lamps) and the boot lighting, that each globe
>> is OK, and then clean its contacts and the receptacle contacts. Note
>> that this must include the fog lamps on the rear. If they are not
>> fitted to the front then dummy resistors are fitted in blank plugs. My
>> plugs/sockets are yellow and contain normal 1 K 1/8 watt resistors (one
>> to each side). Readings of 1K plus or minus 10% are OK - it's not that
>> critical because bulb filaments are not dead accurate anyway - hence the
>> reasonable tolerance.
>>
>> I suggest all these things first, because working on the BFM modules
>> involves a little awkward dismantling and then a sure hand with a fine
>> soldering iron. The modules are labelled "Bulb Relay Module" or
>> suchike. They are a slab shape smaller than a paperback book and in the
>> rear they are bolted to the interior edges of the boot, behind the bulb
>> modules and behind the carpet. One screw off the carpet and pull
>> forward to reveal the module. After unplugging and removing the module,
>> straighten the tabs on the soft aluminium cover and prise off. A
>> printed circuit board bearing relays and other components will be
>> revealled. This board is notorious for "dry" joints. If you are not
>> sure what a dry joint is, then you may be doing the wrong job yourself!
>> Any competent electronics enthusiast or technician should be able to
>> help. Anyway, reflow suspect joints using a fine soldering iron. I
>> think a check of the diodes with an ohm-meter is in order at this
>> stage. They can be tested in circuit. Should be a low resistance one
>> way - very high (or infinity) the other. They are apparently 1N4007 or
>> similar. Very cheap. In an average of 50% of cases this will clear the
>> trouble. Or else move on to the front modules. They are similar in
>> shape and mounted just above and behind the headlamps. Removal is much
>> more fiddly. Disconnect battery negative (after being sure you have any
>> re-activation codes for the audio!). For the right hand side, unbolt
>> and push aside the extrenal relay bank (A/C etc). The bulb relay module
>> is connected by two easy to remove (one black one yellow) connectors,
>> plus a connector to the rear of the headlamp (fiddly to put back - just
>> pull off to remove). One more connection and that is a black wire to
>> the earth, bolted to the frame. It's quite fiddly to get to that and
>> handy to have a magnetic pickup tool to retrieve it when you drop it!
>> Note that there are other connecting tags to that bolt. Should now be
>> able to unbolt and remove the bulb relay (failure) module. Removal of
>> the cover is as before. You will find that inside there is again a
>> printed circuit board, but also another mounted to the top as well.
>> This can be prised off and all contacts on both boards checked for dry
>> joints and once again diodes as well. Replace cover and press in tabs
>> slightly as before. Re-attach the earth wire (*very* important and very
>> fiddly), the headlamp connector (very fiddly - have to work by feel),
>> and then reattach the two connectors. It's so fiddly that I think it is
>> worth checking after doing one, in case that clears it.
>>
>> Apparently, the vast majority of bfm faults will be cleared by one of
>> the above. Well, here's the rub. I've done all these things and
>> *still* I have the rogue warning signal! So, in case you were thinking
>> "he's obviously an expert" by now, you can see that I'm obviously not!
>> I would appreciate any input beyond the above!
>>
>> Hope the above will help some... and that someone will help me!
>>
>> Regards to all
>> Alan
>>
>>


  Reply With Quote
Old 12-16-2005, 21:01   #4 (permalink)
Don Young
Guest
 
Posts: n/a
Re: XJ40 Bulb failure messages (undbelievably another thread!)

Increased click speed of a flasher is definitely an indication of reduced
current through it, so I don't see how increased speed could occur with all
bulbs operating. Sounds like an intermittent fault to me.
Don Young
"WayneC" <WayneC@linkline.moc> wrote in message
news:11q6ovupdbd5r8a@corp.supernews.com...
> Too bad that "very sophisticated" US $2K+ bulb failure system isn't even
> smart enough to point at the problem lamp! Seems to me like it's actually
> pretty danged stupid, considering it's price. Even the old American cars
> of the fifties were smarter: if your dash lights went out and the fuse was
> OK, you pretty much knew a tail light was burnt out. If a front turn
> signal light went out, well, hopefully you don't turn in front of oncoming
> traffic so close up that they'll crash into you if they don't see your
> signal and jam on their brakes! On the Jag, you not only don't know what
> went out, front, rear, or side, but you have to trouble-shoot and
> second-guess the failure monitoring system too!
>
> When do you get the failure warning on your car? Mine (89 XJ40) is random,
> but mostly associated with applying the brakes and/or the left turn
> signal... I'll get one normal turn signal cycle (2 clicks) and then the
> clicking speed doubles (which is the normal audible part of the failure
> alert) and the dash warning appears, and often the turn signals also stop
> blinking at that point (but not always). It does not happen every time I
> use the left turn signal.
>
> As I previously stated on another thread, I have done pretty much
> everything suggested, more than once. That includes renewing all the rear
> bulbs except for license bulbs, cleaning the bulb sockets, resoldering all
> the joints in the rear BFM's, swapping the rear BFM's side-to-side, and
> replacing the left rear BFM with a used BFM.
>
> All my lights are operable (ie, no burnt bulbs), except the left rear turn
> signal sometimes stops operating (both bulbs) when I have this failure
> warning (sometimes it doesn't, but the error warning still shows on the
> dash and the click speed doubles). I haven't changed the front turn signal
> bulbs because the turn signals don't neccessarily need to be on when I get
> the problem (it can happen with the brake lights on), so I assume it's
> associated with the rear; but, I have had the warning pop on when I'm
> simply cruising steady-state on the freeway (rarely, but it HAS happened),
> therefore I intend to change out the front turn signal bulbs too.
>
>
> alan4spamoffd@tpg.com.au wrote:
>> Morning all, from Stinking Hot Australia! (not that I'm complaining)
>>
>> Bulb failure messages! There have been so many threads about this or
>> containing this and other stuff. I have such a problem and thought it
>> might be useful to bring the info to date together once more and seek
>> further info. Apologies if this is old hat to some; it may hep others.
>>
>> An important point to realise is that the bulb failure system on an XJ40
>> is very sophisticated. The condition of all the external bulbs is
>> monitored *even when they are not on!* This is achieved by a group of
>> computerised modules (someone described them as "one at each corner of
>> the car") keeping an eye on the resistance of the bulb circuits using a
>> very low current (and thus voltage, not on as in 12 V). Any failed bulb
>> or circuit will not give a reading within the limits and the failure
>> module signals a fault, even when "off". Of course, the iginition has
>> to be on in order for the whole system to be energised.
>>
>> The small current used in this test is intentionally low enough for eg
>> corroded bulb contacts or even out of spec globes to give the failure
>> signal. Dry joints in the BFM modules themselves can do the same
>> thing. The most common cause is likely to be an actual bulb failure,
>> perhaps a side repeater, one of the number plate lamps, or a bulb
>> overlooked in checking, such as the boot lighting.
>>
>> So, the first thing is the check every external bulb (including reverse
>> lamps, blinkers and brake lamps) and the boot lighting, that each globe
>> is OK, and then clean its contacts and the receptacle contacts. Note
>> that this must include the fog lamps on the rear. If they are not
>> fitted to the front then dummy resistors are fitted in blank plugs. My
>> plugs/sockets are yellow and contain normal 1 K 1/8 watt resistors (one
>> to each side). Readings of 1K plus or minus 10% are OK - it's not that
>> critical because bulb filaments are not dead accurate anyway - hence the
>> reasonable tolerance.
>>
>> I suggest all these things first, because working on the BFM modules
>> involves a little awkward dismantling and then a sure hand with a fine
>> soldering iron. The modules are labelled "Bulb Relay Module" or
>> suchike. They are a slab shape smaller than a paperback book and in the
>> rear they are bolted to the interior edges of the boot, behind the bulb
>> modules and behind the carpet. One screw off the carpet and pull
>> forward to reveal the module. After unplugging and removing the module,
>> straighten the tabs on the soft aluminium cover and prise off. A
>> printed circuit board bearing relays and other components will be
>> revealled. This board is notorious for "dry" joints. If you are not
>> sure what a dry joint is, then you may be doing the wrong job yourself!
>> Any competent electronics enthusiast or technician should be able to
>> help. Anyway, reflow suspect joints using a fine soldering iron. I
>> think a check of the diodes with an ohm-meter is in order at this
>> stage. They can be tested in circuit. Should be a low resistance one
>> way - very high (or infinity) the other. They are apparently 1N4007 or
>> similar. Very cheap. In an average of 50% of cases this will clear the
>> trouble. Or else move on to the front modules. They are similar in
>> shape and mounted just above and behind the headlamps. Removal is much
>> more fiddly. Disconnect battery negative (after being sure you have any
>> re-activation codes for the audio!). For the right hand side, unbolt
>> and push aside the extrenal relay bank (A/C etc). The bulb relay module
>> is connected by two easy to remove (one black one yellow) connectors,
>> plus a connector to the rear of the headlamp (fiddly to put back - just
>> pull off to remove). One more connection and that is a black wire to
>> the earth, bolted to the frame. It's quite fiddly to get to that and
>> handy to have a magnetic pickup tool to retrieve it when you drop it!
>> Note that there are other connecting tags to that bolt. Should now be
>> able to unbolt and remove the bulb relay (failure) module. Removal of
>> the cover is as before. You will find that inside there is again a
>> printed circuit board, but also another mounted to the top as well.
>> This can be prised off and all contacts on both boards checked for dry
>> joints and once again diodes as well. Replace cover and press in tabs
>> slightly as before. Re-attach the earth wire (*very* important and very
>> fiddly), the headlamp connector (very fiddly - have to work by feel),
>> and then reattach the two connectors. It's so fiddly that I think it is
>> worth checking after doing one, in case that clears it.
>>
>> Apparently, the vast majority of bfm faults will be cleared by one of
>> the above. Well, here's the rub. I've done all these things and
>> *still* I have the rogue warning signal! So, in case you were thinking
>> "he's obviously an expert" by now, you can see that I'm obviously not!
>> I would appreciate any input beyond the above!
>>
>> Hope the above will help some... and that someone will help me!
>>
>> Regards to all
>> Alan
>>
>>


  Reply With Quote
Old 12-16-2005, 22:01   #5 (permalink)
WayneC
Guest
 
Posts: n/a
Re: XJ40 Bulb failure messages (undbelievably another thread!)

Don Young wrote:
> A technique I have found useful in troubleshooting intermittent faults is to
> isolate each wire and check its continuity under a fairly heavy load. Such a
> load can be a turn or stop lamp fed by 12 volts. This will nearly always
> find any loose, corroded, or otherwise poor connections. I found a badly
> corroded wire under the floor carpet by this method. Be sure to disconnect
> anything else from the wire under test and be alert for signs of overheating
> if the lamp does not burn or flickers.


Don, I am not sure how one does this on something like the wiring
harness that goes to the BFM's. Could you expand on that a bit? There
are a lot of wires in all those BFM connectors, and knowing which ones
carry switched current and which are ground (and when) is difficult to
determine, not to mention that you have no idea whether a particular
wire is connected to something else in the electrical system upstream of
where you are testing. And what are you looking for, a dim glow from the
test stoplight bulb?


Some very obscure problems can be due
> to poor contacts in plugs and sockets. Sometimes the socket contacts will be
> slightly spread. You can measure the pin and use a wire or drill bit of the
> same or slightly smaller size to check the tension of the sockets.


Here again, I am a bit unclear... "socket" usually refers to a bulb base
connector, but I'm guessing you didn't mean a bulb base... do you mean
the harness connector's female side? The pins can be difficult to
measure when they are encased inside a plastic connector housing.

BTW, one other thing I tried that bugs me... I tested both rear fog
light sockets and got no power reading at either, with or without the
foglight dash switch activated (but, as I write this, although I think I
did, I am not positive I tested with the ignition both off and on, so I
need to revisit that test). I thought I might also try disconnecting the
harness from those fog lamps (at the BFM end, if possible) to see if
that affects anything.

> Don Young
> "WayneC" <WayneC@linkline.moc> wrote in message
> news:11q6ovupdbd5r8a@corp.supernews.com...
>
>>Too bad that "very sophisticated" US $2K+ bulb failure system isn't even
>>smart enough to point at the problem lamp! Seems to me like it's actually
>>pretty danged stupid, considering it's price. Even the old American cars
>>of the fifties were smarter: if your dash lights went out and the fuse was
>>OK, you pretty much knew a tail light was burnt out. If a front turn
>>signal light went out, well, hopefully you don't turn in front of oncoming
>>traffic so close up that they'll crash into you if they don't see your
>>signal and jam on their brakes! On the Jag, you not only don't know what
>>went out, front, rear, or side, but you have to trouble-shoot and
>>second-guess the failure monitoring system too!
>>
>>When do you get the failure warning on your car? Mine (89 XJ40) is random,
>>but mostly associated with applying the brakes and/or the left turn
>>signal... I'll get one normal turn signal cycle (2 clicks) and then the
>>clicking speed doubles (which is the normal audible part of the failure
>>alert) and the dash warning appears, and often the turn signals also stop
>>blinking at that point (but not always). It does not happen every time I
>>use the left turn signal.
>>
>>As I previously stated on another thread, I have done pretty much
>>everything suggested, more than once. That includes renewing all the rear
>>bulbs except for license bulbs, cleaning the bulb sockets, resoldering all
>>the joints in the rear BFM's, swapping the rear BFM's side-to-side, and
>>replacing the left rear BFM with a used BFM.
>>
>>All my lights are operable (ie, no burnt bulbs), except the left rear turn
>>signal sometimes stops operating (both bulbs) when I have this failure
>>warning (sometimes it doesn't, but the error warning still shows on the
>>dash and the click speed doubles). I haven't changed the front turn signal
>>bulbs because the turn signals don't neccessarily need to be on when I get
>>the problem (it can happen with the brake lights on), so I assume it's
>>associated with the rear; but, I have had the warning pop on when I'm
>>simply cruising steady-state on the freeway (rarely, but it HAS happened),
>>therefore I intend to change out the front turn signal bulbs too.
>>
>>
>>alan4spamoffd@tpg.com.au wrote:
>>
>>>Morning all, from Stinking Hot Australia! (not that I'm complaining)
>>>
>>>Bulb failure messages! There have been so many threads about this or
>>>containing this and other stuff. I have such a problem and thought it
>>>might be useful to bring the info to date together once more and seek
>>>further info. Apologies if this is old hat to some; it may hep others.
>>>
>>>An important point to realise is that the bulb failure system on an XJ40
>>>is very sophisticated. The condition of all the external bulbs is
>>>monitored *even when they are not on!* This is achieved by a group of
>>>computerised modules (someone described them as "one at each corner of
>>>the car") keeping an eye on the resistance of the bulb circuits using a
>>>very low current (and thus voltage, not on as in 12 V). Any failed bulb
>>>or circuit will not give a reading within the limits and the failure
>>>module signals a fault, even when "off". Of course, the iginition has
>>>to be on in order for the whole system to be energised.
>>>
>>>The small current used in this test is intentionally low enough for eg
>>>corroded bulb contacts or even out of spec globes to give the failure
>>>signal. Dry joints in the BFM modules themselves can do the same
>>>thing. The most common cause is likely to be an actual bulb failure,
>>>perhaps a side repeater, one of the number plate lamps, or a bulb
>>>overlooked in checking, such as the boot lighting.
>>>
>>>So, the first thing is the check every external bulb (including reverse
>>>lamps, blinkers and brake lamps) and the boot lighting, that each globe
>>>is OK, and then clean its contacts and the receptacle contacts. Note
>>>that this must include the fog lamps on the rear. If they are not
>>>fitted to the front then dummy resistors are fitted in blank plugs. My
>>>plugs/sockets are yellow and contain normal 1 K 1/8 watt resistors (one
>>>to each side). Readings of 1K plus or minus 10% are OK - it's not that
>>>critical because bulb filaments are not dead accurate anyway - hence the
>>>reasonable tolerance.
>>>
>>>I suggest all these things first, because working on the BFM modules
>>>involves a little awkward dismantling and then a sure hand with a fine
>>>soldering iron. The modules are labelled "Bulb Relay Module" or
>>>suchike. They are a slab shape smaller than a paperback book and in the
>>>rear they are bolted to the interior edges of the boot, behind the bulb
>>>modules and behind the carpet. One screw off the carpet and pull
>>>forward to reveal the module. After unplugging and removing the module,
>>>straighten the tabs on the soft aluminium cover and prise off. A
>>>printed circuit board bearing relays and other components will be
>>>revealled. This board is notorious for "dry" joints. If you are not
>>>sure what a dry joint is, then you may be doing the wrong job yourself!
>>>Any competent electronics enthusiast or technician should be able to
>>>help. Anyway, reflow suspect joints using a fine soldering iron. I
>>>think a check of the diodes with an ohm-meter is in order at this
>>>stage. They can be tested in circuit. Should be a low resistance one
>>>way - very high (or infinity) the other. They are apparently 1N4007 or
>>>similar. Very cheap. In an average of 50% of cases this will clear the
>>>trouble. Or else move on to the front modules. They are similar in
>>>shape and mounted just above and behind the headlamps. Removal is much
>>>more fiddly. Disconnect battery negative (after being sure you have any
>>>re-activation codes for the audio!). For the right hand side, unbolt
>>>and push aside the extrenal relay bank (A/C etc). The bulb relay module
>>>is connected by two easy to remove (one black one yellow) connectors,
>>>plus a connector to the rear of the headlamp (fiddly to put back - just
>>>pull off to remove). One more connection and that is a black wire to
>>>the earth, bolted to the frame. It's quite fiddly to get to that and
>>>handy to have a magnetic pickup tool to retrieve it when you drop it!
>>>Note that there are other connecting tags to that bolt. Should now be
>>>able to unbolt and remove the bulb relay (failure) module. Removal of
>>>the cover is as before. You will find that inside there is again a
>>>printed circuit board, but also another mounted to the top as well.
>>>This can be prised off and all contacts on both boards checked for dry
>>>joints and once again diodes as well. Replace cover and press in tabs
>>>slightly as before. Re-attach the earth wire (*very* important and very
>>>fiddly), the headlamp connector (very fiddly - have to work by feel),
>>>and then reattach the two connectors. It's so fiddly that I think it is
>>>worth checking after doing one, in case that clears it.
>>>
>>>Apparently, the vast majority of bfm faults will be cleared by one of
>>>the above. Well, here's the rub. I've done all these things and
>>>*still* I have the rogue warning signal! So, in case you were thinking
>>>"he's obviously an expert" by now, you can see that I'm obviously not!
>>>I would appreciate any input beyond the above!
>>>
>>>Hope the above will help some... and that someone will help me!
>>>
>>>Regards to all
>>>Alan
>>>
>>>

>
>

  Reply With Quote
Old 12-17-2005, 12:01   #6 (permalink)
alan4spamoffd@tpg.com.au
Guest
 
Posts: n/a
Re: XJ40 Bulb failure messages (undbelievably another thread!)

WayneC wrote:

> ...When do you get the failure warning on your car?...


All the time. Have had a double speed blink sound too (but ther actual blinks
were normal), on TWO bfms, but swapping out to a third cured that. Still have
the failure warning signal though.

  Reply With Quote
Old 12-17-2005, 22:01   #7 (permalink)
Don Young
Guest
 
Posts: n/a
Re: XJ40 Bulb failure messages (undbelievably another thread!)

This is only useful when you have a good wiring diagram and/or a suspect
wire, neither of which probably apply in this case. What you would be
looking for would be a bright full voltage glow since you would be using the
suspected wire to carry the bulb current. It is too risky if there might be
something unknown connected to the wire. The comment about the plugs and
sockets might help, as a lot of obscure and intermittent problems are caused
by bad contacts. What seems to be missing is a thorough and explicit
description of the functioning of these modules.
Don Young
"WayneC" <WayneC@linkline.moc> wrote in message
news:11q759nokhod475@corp.supernews.com...
> Don Young wrote:
>> A technique I have found useful in troubleshooting intermittent faults is
>> to isolate each wire and check its continuity under a fairly heavy load.
>> Such a load can be a turn or stop lamp fed by 12 volts. This will nearly
>> always find any loose, corroded, or otherwise poor connections. I found a
>> badly corroded wire under the floor carpet by this method. Be sure to
>> disconnect anything else from the wire under test and be alert for signs
>> of overheating if the lamp does not burn or flickers.

>
> Don, I am not sure how one does this on something like the wiring harness
> that goes to the BFM's. Could you expand on that a bit? There are a lot of
> wires in all those BFM connectors, and knowing which ones carry switched
> current and which are ground (and when) is difficult to determine, not to
> mention that you have no idea whether a particular wire is connected to
> something else in the electrical system upstream of where you are testing.
> And what are you looking for, a dim glow from the test stoplight bulb?
>
>
> Some very obscure problems can be due
>> to poor contacts in plugs and sockets. Sometimes the socket contacts will
>> be slightly spread. You can measure the pin and use a wire or drill bit
>> of the same or slightly smaller size to check the tension of the sockets.

>
> Here again, I am a bit unclear... "socket" usually refers to a bulb base
> connector, but I'm guessing you didn't mean a bulb base... do you mean the
> harness connector's female side? The pins can be difficult to measure when
> they are encased inside a plastic connector housing.
>
> BTW, one other thing I tried that bugs me... I tested both rear fog light
> sockets and got no power reading at either, with or without the foglight
> dash switch activated (but, as I write this, although I think I did, I am
> not positive I tested with the ignition both off and on, so I need to
> revisit that test). I thought I might also try disconnecting the harness
> from those fog lamps (at the BFM end, if possible) to see if that affects
> anything.
>
>> Don Young
>> "WayneC" <WayneC@linkline.moc> wrote in message
>> news:11q6ovupdbd5r8a@corp.supernews.com...
>>
>>>Too bad that "very sophisticated" US $2K+ bulb failure system isn't even
>>>smart enough to point at the problem lamp! Seems to me like it's actually
>>>pretty danged stupid, considering it's price. Even the old American cars
>>>of the fifties were smarter: if your dash lights went out and the fuse
>>>was OK, you pretty much knew a tail light was burnt out. If a front turn
>>>signal light went out, well, hopefully you don't turn in front of
>>>oncoming traffic so close up that they'll crash into you if they don't
>>>see your signal and jam on their brakes! On the Jag, you not only don't
>>>know what went out, front, rear, or side, but you have to trouble-shoot
>>>and second-guess the failure monitoring system too!
>>>
>>>When do you get the failure warning on your car? Mine (89 XJ40) is
>>>random, but mostly associated with applying the brakes and/or the left
>>>turn signal... I'll get one normal turn signal cycle (2 clicks) and then
>>>the clicking speed doubles (which is the normal audible part of the
>>>failure alert) and the dash warning appears, and often the turn signals
>>>also stop blinking at that point (but not always). It does not happen
>>>every time I use the left turn signal.
>>>
>>>As I previously stated on another thread, I have done pretty much
>>>everything suggested, more than once. That includes renewing all the rear
>>>bulbs except for license bulbs, cleaning the bulb sockets, resoldering
>>>all the joints in the rear BFM's, swapping the rear BFM's side-to-side,
>>>and replacing the left rear BFM with a used BFM.
>>>
>>>All my lights are operable (ie, no burnt bulbs), except the left rear
>>>turn signal sometimes stops operating (both bulbs) when I have this
>>>failure warning (sometimes it doesn't, but the error warning still shows
>>>on the dash and the click speed doubles). I haven't changed the front
>>>turn signal bulbs because the turn signals don't neccessarily need to be
>>>on when I get the problem (it can happen with the brake lights on), so I
>>>assume it's associated with the rear; but, I have had the warning pop on
>>>when I'm simply cruising steady-state on the freeway (rarely, but it HAS
>>>happened), therefore I intend to change out the front turn signal bulbs
>>>too.
>>>
>>>
>>>alan4spamoffd@tpg.com.au wrote:
>>>
>>>>Morning all, from Stinking Hot Australia! (not that I'm complaining)
>>>>
>>>>Bulb failure messages! There have been so many threads about this or
>>>>containing this and other stuff. I have such a problem and thought it
>>>>might be useful to bring the info to date together once more and seek
>>>>further info. Apologies if this is old hat to some; it may hep others.
>>>>
>>>>An important point to realise is that the bulb failure system on an XJ40
>>>>is very sophisticated. The condition of all the external bulbs is
>>>>monitored *even when they are not on!* This is achieved by a group of
>>>>computerised modules (someone described them as "one at each corner of
>>>>the car") keeping an eye on the resistance of the bulb circuits using a
>>>>very low current (and thus voltage, not on as in 12 V). Any failed bulb
>>>>or circuit will not give a reading within the limits and the failure
>>>>module signals a fault, even when "off". Of course, the iginition has
>>>>to be on in order for the whole system to be energised.
>>>>
>>>>The small current used in this test is intentionally low enough for eg
>>>>corroded bulb contacts or even out of spec globes to give the failure
>>>>signal. Dry joints in the BFM modules themselves can do the same
>>>>thing. The most common cause is likely to be an actual bulb failure,
>>>>perhaps a side repeater, one of the number plate lamps, or a bulb
>>>>overlooked in checking, such as the boot lighting.
>>>>
>>>>So, the first thing is the check every external bulb (including reverse
>>>>lamps, blinkers and brake lamps) and the boot lighting, that each globe
>>>>is OK, and then clean its contacts and the receptacle contacts. Note
>>>>that this must include the fog lamps on the rear. If they are not
>>>>fitted to the front then dummy resistors are fitted in blank plugs. My
>>>>plugs/sockets are yellow and contain normal 1 K 1/8 watt resistors (one
>>>>to each side). Readings of 1K plus or minus 10% are OK - it's not that
>>>>critical because bulb filaments are not dead accurate anyway - hence the
>>>>reasonable tolerance.
>>>>
>>>>I suggest all these things first, because working on the BFM modules
>>>>involves a little awkward dismantling and then a sure hand with a fine
>>>>soldering iron. The modules are labelled "Bulb Relay Module" or
>>>>suchike. They are a slab shape smaller than a paperback book and in the
>>>>rear they are bolted to the interior edges of the boot, behind the bulb
>>>>modules and behind the carpet. One screw off the carpet and pull
>>>>forward to reveal the module. After unplugging and removing the module,
>>>>straighten the tabs on the soft aluminium cover and prise off. A
>>>>printed circuit board bearing relays and other components will be
>>>>revealled. This board is notorious for "dry" joints. If you are not
>>>>sure what a dry joint is, then you may be doing the wrong job yourself!
>>>>Any competent electronics enthusiast or technician should be able to
>>>>help. Anyway, reflow suspect joints using a fine soldering iron. I
>>>>think a check of the diodes with an ohm-meter is in order at this
>>>>stage. They can be tested in circuit. Should be a low resistance one
>>>>way - very high (or infinity) the other. They are apparently 1N4007 or
>>>>similar. Very cheap. In an average of 50% of cases this will clear the
>>>>trouble. Or else move on to the front modules. They are similar in
>>>>shape and mounted just above and behind the headlamps. Removal is much
>>>>more fiddly. Disconnect battery negative (after being sure you have any
>>>>re-activation codes for the audio!). For the right hand side, unbolt
>>>>and push aside the extrenal relay bank (A/C etc). The bulb relay module
>>>>is connected by two easy to remove (one black one yellow) connectors,
>>>>plus a connector to the rear of the headlamp (fiddly to put back - just
>>>>pull off to remove). One more connection and that is a black wire to
>>>>the earth, bolted to the frame. It's quite fiddly to get to that and
>>>>handy to have a magnetic pickup tool to retrieve it when you drop it!
>>>>Note that there are other connecting tags to that bolt. Should now be
>>>>able to unbolt and remove the bulb relay (failure) module. Removal of
>>>>the cover is as before. You will find that inside there is again a
>>>>printed circuit board, but also another mounted to the top as well.
>>>>This can be prised off and all contacts on both boards checked for dry
>>>>joints and once again diodes as well. Replace cover and press in tabs
>>>>slightly as before. Re-attach the earth wire (*very* important and very
>>>>fiddly), the headlamp connector (very fiddly - have to work by feel),
>>>>and then reattach the two connectors. It's so fiddly that I think it is
>>>>worth checking after doing one, in case that clears it.
>>>>
>>>>Apparently, the vast majority of bfm faults will be cleared by one of
>>>>the above. Well, here's the rub. I've done all these things and
>>>>*still* I have the rogue warning signal! So, in case you were thinking
>>>>"he's obviously an expert" by now, you can see that I'm obviously not!
>>>>I would appreciate any input beyond the above!
>>>>
>>>>Hope the above will help some... and that someone will help me!
>>>>
>>>>Regards to all
>>>>Alan
>>>>
>>>>

>>


  Reply With Quote
Old 12-18-2005, 12:02   #8 (permalink)
nospam@nospam.com
Guest
 
Posts: n/a
Re: XJ40 Bulb failure messages (undbelievably another thread!)

I'm afraid a great deal is mssing in the Haynes book. But a poster on the
Jaglovers site (who still has a problem) makes agood job of explaining how the
bulb warning system works.

Don Young wrote:

> This is only useful when you have a good wiring diagram and/or a suspect
> wire, neither of which probably apply in this case. What you would be
> looking for would be a bright full voltage glow since you would be using the
> suspected wire to carry the bulb current. It is too risky if there might be
> something unknown connected to the wire. The comment about the plugs and
> sockets might help, as a lot of obscure and intermittent problems are caused
> by bad contacts. What seems to be missing is a thorough and explicit
> description of the functioning of these modules.
> Don Young
> "WayneC" <WayneC@linkline.moc> wrote in message
> news:11q759nokhod475@corp.supernews.com...
> > Don Young wrote:
> >> A technique I have found useful in troubleshooting intermittent faults is
> >> to isolate each wire and check its continuity under a fairly heavy load.
> >> Such a load can be a turn or stop lamp fed by 12 volts. This will nearly
> >> always find any loose, corroded, or otherwise poor connections. I found a
> >> badly corroded wire under the floor carpet by this method. Be sure to
> >> disconnect anything else from the wire under test and be alert for signs
> >> of overheating if the lamp does not burn or flickers.

> >
> > Don, I am not sure how one does this on something like the wiring harness
> > that goes to the BFM's. Could you expand on that a bit? There are a lot of
> > wires in all those BFM connectors, and knowing which ones carry switched
> > current and which are ground (and when) is difficult to determine, not to
> > mention that you have no idea whether a particular wire is connected to
> > something else in the electrical system upstream of where you are testing.
> > And what are you looking for, a dim glow from the test stoplight bulb?
> >
> >
> > Some very obscure problems can be due
> >> to poor contacts in plugs and sockets. Sometimes the socket contacts will
> >> be slightly spread. You can measure the pin and use a wire or drill bit
> >> of the same or slightly smaller size to check the tension of the sockets.

> >
> > Here again, I am a bit unclear... "socket" usually refers to a bulb base
> > connector, but I'm guessing you didn't mean a bulb base... do you mean the
> > harness connector's female side? The pins can be difficult to measure when
> > they are encased inside a plastic connector housing.
> >
> > BTW, one other thing I tried that bugs me... I tested both rear fog light
> > sockets and got no power reading at either, with or without the foglight
> > dash switch activated (but, as I write this, although I think I did, I am
> > not positive I tested with the ignition both off and on, so I need to
> > revisit that test). I thought I might also try disconnecting the harness
> > from those fog lamps (at the BFM end, if possible) to see if that affects
> > anything.
> >
> >> Don Young
> >> "WayneC" <WayneC@linkline.moc> wrote in message
> >> news:11q6ovupdbd5r8a@corp.supernews.com...
> >>
> >>>Too bad that "very sophisticated" US $2K+ bulb failure system isn't even
> >>>smart enough to point at the problem lamp! Seems to me like it's actually
> >>>pretty danged stupid, considering it's price. Even the old American cars
> >>>of the fifties were smarter: if your dash lights went out and the fuse
> >>>was OK, you pretty much knew a tail light was burnt out. If a front turn
> >>>signal light went out, well, hopefully you don't turn in front of
> >>>oncoming traffic so close up that they'll crash into you if they don't
> >>>see your signal and jam on their brakes! On the Jag, you not only don't
> >>>know what went out, front, rear, or side, but you have to trouble-shoot
> >>>and second-guess the failure monitoring system too!
> >>>
> >>>When do you get the failure warning on your car? Mine (89 XJ40) is
> >>>random, but mostly associated with applying the brakes and/or the left
> >>>turn signal... I'll get one normal turn signal cycle (2 clicks) and then
> >>>the clicking speed doubles (which is the normal audible part of the
> >>>failure alert) and the dash warning appears, and often the turn signals
> >>>also stop blinking at that point (but not always). It does not happen
> >>>every time I use the left turn signal.
> >>>
> >>>As I previously stated on another thread, I have done pretty much
> >>>everything suggested, more than once. That includes renewing all the rear
> >>>bulbs except for license bulbs, cleaning the bulb sockets, resoldering
> >>>all the joints in the rear BFM's, swapping the rear BFM's side-to-side,
> >>>and replacing the left rear BFM with a used BFM.
> >>>
> >>>All my lights are operable (ie, no burnt bulbs), except the left rear
> >>>turn signal sometimes stops operating (both bulbs) when I have this
> >>>failure warning (sometimes it doesn't, but the error warning still shows
> >>>on the dash and the click speed doubles). I haven't changed the front
> >>>turn signal bulbs because the turn signals don't neccessarily need to be
> >>>on when I get the problem (it can happen with the brake lights on), so I
> >>>assume it's associated with the rear; but, I have had the warning pop on
> >>>when I'm simply cruising steady-state on the freeway (rarely, but it HAS
> >>>happened), therefore I intend to change out the front turn signal bulbs
> >>>too.
> >>>
> >>>
> >>>alan4spamoffd@tpg.com.au wrote:
> >>>
> >>>>Morning all, from Stinking Hot Australia! (not that I'm complaining)
> >>>>
> >>>>Bulb failure messages! There have been so many threads about this or
> >>>>containing this and other stuff. I have such a problem and thought it
> >>>>might be useful to bring the info to date together once more and seek
> >>>>further info. Apologies if this is old hat to some; it may hep others.
> >>>>
> >>>>An important point to realise is that the bulb failure system on an XJ40
> >>>>is very sophisticated. The condition of all the external bulbs is
> >>>>monitored *even when they are not on!* This is achieved by a group of
> >>>>computerised modules (someone described them as "one at each corner of
> >>>>the car") keeping an eye on the resistance of the bulb circuits using a
> >>>>very low current (and thus voltage, not on as in 12 V). Any failed bulb
> >>>>or circuit will not give a reading within the limits and the failure
> >>>>module signals a fault, even when "off". Of course, the iginition has
> >>>>to be on in order for the whole system to be energised.
> >>>>
> >>>>The small current used in this test is intentionally low enough for eg
> >>>>corroded bulb contacts or even out of spec globes to give the failure
> >>>>signal. Dry joints in the BFM modules themselves can do the same
> >>>>thing. The most common cause is likely to be an actual bulb failure,
> >>>>perhaps a side repeater, one of the number plate lamps, or a bulb
> >>>>overlooked in checking, such as the boot lighting.
> >>>>
> >>>>So, the first thing is the check every external bulb (including reverse
> >>>>lamps, blinkers and brake lamps) and the boot lighting, that each globe
> >>>>is OK, and then clean its contacts and the receptacle contacts. Note
> >>>>that this must include the fog lamps on the rear. If they are not
> >>>>fitted to the front then dummy resistors are fitted in blank plugs. My
> >>>>plugs/sockets are yellow and contain normal 1 K 1/8 watt resistors (one
> >>>>to each side). Readings of 1K plus or minus 10% are OK - it's not that
> >>>>critical because bulb filaments are not dead accurate anyway - hence the
> >>>>reasonable tolerance.
> >>>>
> >>>>I suggest all these things first, because working on the BFM modules
> >>>>involves a little awkward dismantling and then a sure hand with a fine
> >>>>soldering iron. The modules are labelled "Bulb Relay Module" or
> >>>>suchike. They are a slab shape smaller than a paperback book and in the
> >>>>rear they are bolted to the interior edges of the boot, behind the bulb
> >>>>modules and behind the carpet. One screw off the carpet and pull
> >>>>forward to reveal the module. After unplugging and removing the module,
> >>>>straighten the tabs on the soft aluminium cover and prise off. A
> >>>>printed circuit board bearing relays and other components will be
> >>>>revealled. This board is notorious for "dry" joints. If you are not
> >>>>sure what a dry joint is, then you may be doing the wrong job yourself!
> >>>>Any competent electronics enthusiast or technician should be able to
> >>>>help. Anyway, reflow suspect joints using a fine soldering iron. I
> >>>>think a check of the diodes with an ohm-meter is in order at this
> >>>>stage. They can be tested in circuit. Should be a low resistance one
> >>>>way - very high (or infinity) the other. They are apparently 1N4007 or
> >>>>similar. Very cheap. In an average of 50% of cases this will clear the
> >>>>trouble. Or else move on to the front modules. They are similar in
> >>>>shape and mounted just above and behind the headlamps. Removal is much
> >>>>more fiddly. Disconnect battery negative (after being sure you have any
> >>>>re-activation codes for the audio!). For the right hand side, unbolt
> >>>>and push aside the extrenal relay bank (A/C etc). The bulb relay module
> >>>>is connected by two easy to remove (one black one yellow) connectors,
> >>>>plus a connector to the rear of the headlamp (fiddly to put back - just
> >>>>pull off to remove). One more connection and that is a black wire to
> >>>>the earth, bolted to the frame. It's quite fiddly to get to that and
> >>>>handy to have a magnetic pickup tool to retrieve it when you drop it!
> >>>>Note that there are other connecting tags to that bolt. Should now be
> >>>>able to unbolt and remove the bulb relay (failure) module. Removal of
> >>>>the cover is as before. You will find that inside there is again a
> >>>>printed circuit board, but also another mounted to the top as well.
> >>>>This can be prised off and all contacts on both boards checked for dry
> >>>>joints and once again diodes as well. Replace cover and press in tabs
> >>>>slightly as before. Re-attach the earth wire (*very* important and very
> >>>>fiddly), the headlamp connector (very fiddly - have to work by feel),
> >>>>and then reattach the two connectors. It's so fiddly that I think it is
> >>>>worth checking after doing one, in case that clears it.
> >>>>
> >>>>Apparently, the vast majority of bfm faults will be cleared by one of
> >>>>the above. Well, here's the rub. I've done all these things and
> >>>>*still* I have the rogue warning signal! So, in case you were thinking
> >>>>"he's obviously an expert" by now, you can see that I'm obviously not!
> >>>>I would appreciate any input beyond the above!
> >>>>
> >>>>Hope the above will help some... and that someone will help me!
> >>>>
> >>>>Regards to all
> >>>>Alan
> >>>>
> >>>>
> >>




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