Re: ford focus heater fault
Thanks very much for the advice, much appreciated. I should have made
it clear that the blower only works on the second fastest setting
I will take the advice on board and investigate further.
Alan <email@example.com> wrote in message news:<K9YmVVGazjJCFwoa@amacleod.clara.co.uk>...
> In message <firstname.lastname@example.org>, lennario
> <email@example.com> wrote
> >We have recently bought a 5 year old Focus and it has just developed a
> >fault with the heater. It only works on number 3. Does anyone have any
> >idea what may have caused the fault and whether it might be easier to
> Do you mean the heater or the blower fan.?
> If you mean that the blower fan only works on the fastest setting then
> it may be an easy DIY fix if you have some skill with a soldering
> iron/gun and a multi-meter.
> If the fan only works on the fastest speed there is a good chance that a
> thermal fuse has failed. Unfortunately the thermal fuse is part of the
> blower resistor assembly.
> Note: The thermal fuse is different to those fitted in the fuse boxes.
> The speed of the fan in the first three positions is controlled by a
> bank of resistors which are relatively large and get hot. The thermal
> fuse is in series with these resistors and physically almost touching
> them. When the fuse blows the first three position don't work. In the
> final switch position the battery voltage goes straight across the
> motor, bypassing resistors and thermal fuse network, hence it works.
> The resistor and fuse assembly is usually mounted in the blower motor
> air stream and I believe that you can get to the resistor assembly by
> removing the blower motor in the Focus. Release the glove box by flexing
> the back plastic sides (a _tiny_ bit of force may be required). The
> glove box then hangs out of the way and you can see the blower motor and
> Below is what I have advised before but it is worth getting a second or
> third opinion from the news archives at Google groups.
> Type 'thermal fuse blower motor' into the search box (without the
> quotation marks).
> The advice given for other cars is valid.
> The fuse is a two legged device which when it reaches a preset
> temperature blows permanently open circuit.
> I would assume that the way the module is constructed that the fuse
> alone isn't a replaceable part and that a dealer would charge for the
> whole module. However it is a do-it-yourself fix if you can find the
> motor 'resistor module' and have some basic electrical soldering
> In the UK the a replacement thermal fuse (for the do-it-yourself repair)
> can be obtained quite cheaply (0.5 GPB or less than $1 US) from
> electronic component stores.
> I've included the references to the devices plus a circuit of the blower
> motor circuit on
> < http://www.amacleod.clara.co.uk/focus/index.htm>
> When buying the replacement fuses the one you want is probably towards
> the higher end of the temperature range (150+ degrees C).
> Before replacing the thermal fuse check it with a meter to see if it
> open circuit or temporality short across it to see if the motor works on
> the lower speed settings.
> Despite the warnings about not to solder to the leads of a thermal fuse
> I've successfully used a high wattage soldering gun and _quickly_
> soldered at the ends of the leads. Obviously as it is a one time thermal
> fuse leaving the soldering iron in contact too long will heat up the
> whole device to a temperature where the fuse blows. As they are cheap it
> may be worth ordering a couple - just in case :) You could attach a
> crocodile clip or bulldog clip as a heat-sink to the body of the fuse
> while soldering to reduce the heat build-up.
> Cut the old thermal fuse out but leave about quarter of an inch of the
> lead on each side that is crimped to the terminals on the assembly.
> Leaving a bit of the old lead in place will make soldering the new
> component easier. Soldering to the terminal post is difficult unless you
> can clean it up with a small file.
> The problem may have been caused as a result of water getting into the
> system and the blower motor not running as smoothly as it should. On
> previous cars where I have fixed identical problems the motor shafts
> were rusty and some lubrication (ONE DROP of engine oil from the
> dip-stick) was applied to the motor shaft bearing area.
> Also consider that it is not unknown for the switch to mechanically