Re: XJ40 Bulb Failure Module & door lock problems
Based on Webserve's questions and comments about my lock problem, I
decided I'd better do more fact-finding about the symptoms of my lock
issue, so played with the locks a bit today, and found I was wrong on
some counts. Here is what I found today:
Summary of today's testing:
Manipulating either front door lock using the key never causes the
opposite front door to lock or unlock, but will lock or unlock the rear
and will close all windows and the sunroof.
My dash rocker switch does work, but only on the rear doors,
all windows, and the sunroof, ...NOT on the front doors.
Rear doors cannot be LOCKED by manipulating either
front door lock plunger.
Once locked by the dash rocker switch, the rear doors can be
unlocked by manipulating a front door lock plunger, but only if the
opposite front door plunger is already in the locked (down) position.
The ignition key does not cause any door locks to be locked or unlocked
So, does anyone have any ideas what lock system component can cause this???
Short version results of my tests today....
1) with the car parked and all doors locked in each case:
- If I unlock the driver door with the key,
both rear doors unlock (passenger front stays locked)
- If I unlock the passenger front door with the key,
both rear doors unlock (driver front stays locked)
with the car parked and all doors now unlocked in each case:
- If I lock the driver door with the key, both rear doors lock
(passenger door stays unlocked), and if I keep the key turned,
all windows and the sunroof lock
- If I lock the passenger door with the key, both rear doors lock
(driver door stays unlocked), and if I keep the key turned,
all windows and the sunroof lock
3) sitting inside the car with the ignition key off, rear doors unlocked
- dash rocker switch does nothing (probably normal)
- cycling either front door lock plunger does nothing
4) sitting in the car with the ignition key on,
driver and rear doors unlocked, front passenger door locked
- cycling either front door lock plunger does nothing
- pushing the dash rocker swich locks the rear doors
and rolls up the windows and closes the sunroof
- cycling either front door plunger will unlock the rear doors
but does not lock them
so, I can only UNLOCK the rear doors by manipulating the front
door plunger, I cannot lock them except by using the dash
5) further testing showed that the position of the opposite
front door lock plunger matters, ie, the plunger on the door
opposite to the one I try to manipulate...
If the opposite door plunger is up, manipulating the other door
plunger does nothing (ie, maybe the system thinks all
the doors are already unlocked, and so it will not unlock
the rear doors).
This seems to be true whether or not the ignition is on
6) I did not find a case where the passenger door plunger came up
by itself; ie, when the ignition is on or the car is started;
I could have sworn that happens frequently. I am either
mistaken and it happens only when a passenger leaves the door
unlocked on exiting, or it just didn't occur during my testing
today. I do know I frequently walk around the car (or reach
across) to lock the front passenger door when I am alone.
WayneC previously wrote:
> I am trying to make a new thread to get this stuff out of the "Second
> Differential" thread. Sorry, I should have done this in the first place.
> Here are the posts so far (copied from the Second Differential thread:
> WayneC said...
> I've been chasing 2 problems for years on my 89 XJ40 that are driving me
> nuts, and haven't found answers by posting here or elsewhere.
> 1. Bulb failure message: comes on sometimes with stop lights and
> frequently if turn signal is also on (accompanied by double-speed turn
> signal noise, and sometimes the left turn signal bulbs cease blinking
> when this happens, sometimes they continue blinking normally); it can
> occur spontaneoulsly (but seldom) like when just cruising on the freeway
> with no lights turned on. Have replaced all rear bulbs, cleaned sockets,
> swapped rear bulb failure modules, resoldered all joints in both rear
> bulb failure modules, and replaced one module. Nothing helped.
> 2. Door locks: I never had a remote so we are talking manual by key or
> the plunger. They used to work fine. Now unlocking either front door
> unlocks the rear doors. Locking either front door locks the rear doors.
> Neither front door lock affects the other front door lock. The dash lock
> button does nothing except elicit a faint clicking noise. All doors lock
> when the ignition is turned on and unlock when the ignition key is
> turned off (almost always... but the passenger door doesn't always
> unlock). Result is I have to walk around the car to lock the passenger
> door nearly every time I park (or stretch way across and push the
> plunger), or to let a passenger into the car. Most components are
> expensive and difficult to replace, and I have no idea how to determine
> which are the bad part(s). I've had both front doors apart several
> times, to no avail (nothing obvious found amiss). I've replaced both
> front door handles (for mechanical failure reasons, and replacement did
> not affect this problem). The fact that the dash button doesn't unlock
> any of the doors is probably a big clue (ie, does it control one door's
> locking motor which in turn affects the others? is it a problem in the
> central door lock control box under the dash?) but I can't follow Jag's
> electrical diagrams well enough to figure it out and don't want to tear
> both front doors apart and replace 2 motors at $160 or so each just to
> see if they are the problem..
> Webserve said (with WayneC answers/remarks interspersed)...
> webserve wrote:
> > Wow, you have done nearly every thing on the BFM unit. Here is what I
> > suggest. Take the Left BFM out again and pull the top circuit board
> off the
> > lower board. Steal one of your wife's nail file emery boards and
> sand all
> > the prong contacts as well as the plug sockets so they all have decent
> > electrical contact.
> I've done the sockets.
> > This is a LIGHT procedure -- do not over do it. Also
> > GENTLY spread the prongs out a bit to make sure there is contact.
> With the
> > intermittent problem you describe, I believe it is a contact problem
> > for the circuit obviously works -- just not all the time.
> I'm not sure which "prongs" you are referring to... in the BFM?
> I have a low confidence level since I've already swapped AND replaced
> that BFM (with another used one). And in fact I bought a second used BFM
> that I haven't tried yet.
> > As for the door locks. This is an obvious electrical problem as well.
> Yeah, but no one knows how to troubleshoot the system.
> > Fortunately, one I have not had to deal with. You problem is not with
> > the actuator
> Yep, I knew that (assuming you mean the mechanical plunger or the switch
> at the key tumbler... which do you mean?
> > for if you turn the correct key -- it locks or unlocks. So all the
> > actuators are working.
> Depends on what you mean by an actuator.. if you mean the switch, yes.
> But, neither front door ever locks without using the key or the manual
> plunger on that same door... turning the key does in fact mechanically
> move the lock plunger on that door. It does not electrically actuate the
> other front door lock. That goes for both front doors, and for unlocking.
> > It seems there is an electrical disconnect between
> > the front door locks and the button. Does the button close the sun
> I'll have to try that... I believe it used to, though I rarely used that
> button; I do recall that it used to lock the doors. The sunroof is
> another (newer) issue, as I need a new headliner... if I open the
> sunroof it hits the hanging material, thus I stopped opening it. I'll
> fix the roofliner as soon as I decide if I'm going to keep this car
> (I've owned it 5 or 6 years, always had the BF messages and mostly
> ignored it, the lock problems are maybe a year old now; my patience is
> wearing thin with those problems)
> > If you get out of the car and hold the key in the lock position in the
> > driver's door do all the doors lock, the windows go up and the sun roof
> > close? Doing that should determine where the problem lies.
> All BUT the passenger front door lock. In fact, after the last time I
> fooled around with the driver door handle, it works TOO good, making it
> just about impossible to leave my windows cracked about half an inch,
> which I like to do (gets hot around here). By the time I can turn the
> key quickly, the mindows are shut.
> > It is odd that your doors all lock and unlock with the ignition -- mine
> > don't.
> I'll have to doublecheck that, I thought they did, perhaps not. I know
> the passenger door often seems to get unlocked (when I haven't any
> passengers) because I keep having to walk around or reach over to lock
> it (the unlocking may happen when the driver door is opened). I think
> the trunk lid gets locked, too, when the ignition is turned on, but I
> won't swear to that.
> I know all the locks are tied together electrically, I just don't know
> the routing... I suspect the dash rocker switch button causes the
> central lock controller under the dash to pass current to ONE of the
> lock motors, either passenger or driver door, and the movement of that
> lock then causes the other 3 to lock. The routing to the other 3 may be
> through the central lock controller, or may not. So I'm thinking I might
> have a problem in the central controller or in one or both of the front
> door lock motors (on the locking side of the circuit), or a bad wire
> contact somewhere. The question is which component is bad (since all are
> expensive to replace), or where is the fault in the wiring.
> > BTW, didn't you move to Ca from Va and sell your XJS or is that
> > a different WayneC??
> Must be a different WayneC, I still have an XJS and I never lived in VA.
> Bought both the XJ40 and XJS after moving here. The XJS is in slightly
> better shape with about 85k miles vs 135k, but it, too, is starting to
> feel it's age (1984).
> Alan said...
> Hmmm... I'm also having frustrating BFM problems. I have a continuous
> BF message flashing in my XJ40 1988 display. It seems that only the
> *front* modules have the add on board that plugs into the other. The
> rear ones are much simpler. I too have tried to clear this BF "fault"
> without success but I haven't yet tried the nailfile trick, I must say.
> I also have a *new* problem which has started since fitting a
> replacement secondhand (right front) module to try and fix the BF
> message (which it didn't) Now if I blink right (or switch on hazards)
> the blinking *sound* is more rapid intermittently but the actual blink
> is OK. I'm concerned that this and the BF message may mask a *real*
> problem when I'm on the road, so would like to cure this. I also have a
> dummy "low windscreen washer" message I'd dearly like to clear, so that
> finally my fault display will be clear until I get a *real* fault. Of
> course, I'd like to do this all yesterday so I'm ready for safe Cristmas
> trip (sigh).