Xsara heater problem

trog1960 · Post by **trog1960** » 25 Feb 2008, 19:31

I've just developed an odd problem with the heater control on my 99 Xsara HDI after a long trip through Europe.
4 position heater (blower) switch suddenly only works on #4 and does nothing on other positions.
I've checked other heater control posts but they all seem to be Xantia related (my other car's a Xantia and has blower control problems as well)
I had a BX before that had blower control problems which I traced to a bad contact on the blower motor transistor.
Does anyone have any suggestions as to where to look on the Xsara for heater control problems

Post by **RichardW** » 26 Feb 2008, 07:43

The car will either be fitted with a resistor pack located somewhere in the air trunking (I'd look under the dash in the passneger foot well) or it may have transistors on the fan itself. Whichever, the control unit has gone phut and needs to be replaced (repair may be possible if it's transistorised on the fan).

a4gom · Post by **a4gom** » 28 Apr 2008, 22:49

Any more info on this, I have the same problem.

I'm no electrician so please excuse the explanation. There are IIRC it looks like there are 8 wires coming from the back of the switch (my switch has 4 settings on ext air, 4 settings on recirculated), 4wires go to the back of a round plastic thing in the heater pipe, 2 go to the motor which operate the flap which controls where the air comes from and 2 wires go to the fan motor. As there are only two wires to the fan motor I am assuming the speed is controlled by voltage and something between the switch and the motor, is it the round plastic thing in the pipe? when I remove it it has a couple or silver spiral wire things on. I've read somewhere else I need to replace a resistor? Is that what these are? If so which one / where from? If not what should I be looking for?

TIA

Clogzz · Post by **Clogzz** » 29 Apr 2008, 13:45

The silver/yellow fuse link is open, causing loss of the lower speeds.
It’s a 170ºC thermal fuse that feeds the dropping resistors for the 3 lower speeds.
Top speed is direct feed without resistors, and that’s why 4th still works.

I’m not writing to replace the link with a failsafe nail, because it’s a safety item, but a momentary bypass will show what the lower speeds are making of it.

a4gom · Post by **a4gom** » 29 Apr 2008, 14:23

Many thanks, so if I get a RA18U from here and solder it in that should sort it ?

Clogzz · Post by **Clogzz** » 29 Apr 2008, 15:22

Yes, close enough.
You may be able to measure the old one before sinking 69 pence in a new one.
As it says there, try crimping it like the old one is, because the solder may melt later.
The heat from the soldering can weaken the new link.
Fuse links sometimes let go for no reason.
If it gets too hot in there, it’s usually caused by low airflow, and also by high fan motor current.
And high current is often caused by restricted airflow.

a4gom · Post by **a4gom** » 29 Apr 2008, 15:31

Not sure how to measure the old one, I have one of those multimeter things with all the settimgs but like I said I'm no electrician.

Low air flow is a definate as I have just removed what was potentially the original filter in the pipe, it was clogged solid!! I need to get a replacement but I have cleaned it up best I can for now with the air hose and its running freely now.

Clogzz · Post by **Clogzz** » 29 Apr 2008, 15:51

Ouch !

Mistake !

It’s 98ºC, not 170ºC, mixed up with something else.
The temperature will be written on the fuse.

The multimeter, any range that gives a full-scale reading when joining the probes will do.
That’s with the motor unplugged.
Link good … full scale.
Link open … nothing.

a4gom · Post by **a4gom** » 29 Apr 2008, 16:11

Thanks, i'll get the old one off and have a look.
Its interesting that someone else on the citroen owners club has suggested part numbers for both Maplins and Farnells which refer to 167degree ones?

Clogzz · Post by **Clogzz** » 29 Apr 2008, 16:42

Just went there, seen that, and am confused even more.

The map showing 98ºC is from the Xantia, same vintage as the Xsara.
There is an earlier resistor block, looking different, probably of BX vintage.
If the fuse can’t be read, Maplin may identify it.
Back tomorrow, it’s late here.

a4gom · Post by **a4gom** » 30 Apr 2008, 09:40

Had a quick look last night, didn't have chance to check with the meter but the link has 169'c on it.

Clogzz · Post by **Clogzz** » 30 Apr 2008, 13:05

Good … good ! No upheaval.

Can’t compare with my own car, it’s got air conditioning, with the transistor drive instead of the resistors.
Looked in BoL 1996, it has the same map as above, saying 98ºC.
That’s another justification to call it the ‘Book of Lies’.

Measuring the link with the speed controller turned off is the same as with the motor unplugged.
When turned off, the link and all the resistors are out of circuit.

a4gom · Post by **a4gom** » 13 May 2008, 23:57

just a quick post for future ref, my existing link had 169 on it, nearest maplins had was 167, i replaced and touch wood its still working fine.