Xantia Air Con Temp/Fan Problems

Richard Gallagher · Post by **Richard Gallagher** » 02 Nov 2003, 23:58

Having just bought a very late Mk 1 Xantia CT Turbo Estate (air con), I have a problem with the heater fan and temperature control. [:(]
When the fan is set to auto and the temperature to a warm position, the fan correctly speeds up in order to reach the temperature quickly. However when set to a cooler temperature the fan just slows down, (despite setting the intake to recycle the hot air inside the car), rather than speeding up to cool the air quickly, like my other Xantia.
Whatever temperature I set, the air coming out of the vents appears warmer than that asked for.[:I]
The air con has just been regassed and cools the air well provided the temperature is set into the minimum, below 18 degrees.
The fan does work on all speeds, so I'm left wondering whether to replace the temperature sensor (fan behind it works) or whether the Bitron sensor has any influence on the above. Is it a air con ECU and where is it situated?
By the way, what does Bitron stand for/mean?

Dave Burns · Post by **Dave Burns** » 03 Nov 2003, 00:30

And whats the machanism for changing to lower temperature from a higher one or vise versa when on auto mode, must have motorised flaps but I have never heard any such things operating on my car.
The bitron controler is a toad to get at being under the nearside head lamp, this I believe is for the aircon and the engine cooling fans only, I think there is a seperate ecu for the interior temperature control though I don't know where it is.
The name Bitron is a manufacturers trade name, much like Lucas, Bosch and the like, you see it on a number of electronic components in the xantia, the one shot window controller is on of them.
Dave

wheeler · Post by **wheeler** » 03 Nov 2003, 01:47

i THINK the climate control is ECU behind & to the right of the glovebox,not 100% though.
thats definitely where it is on a xsara.
it is small stepper motors that operate the mixer flaps (they are very quiet).
do you still have the other xantia ? you could try swapping parts off it i.e. interior temp sensor,ECU,evaporator temp sensor.
like dave says the bitron box is for the cooling fans,i think the only thing to do with aircon it does it cut the compressor off if the engine temp gets too high.

Richard Gallagher · Post by **Richard Gallagher** » 03 Nov 2003, 02:14

Thaanks chaps I do still have the other Xantia, I'll swap the temp sensor and see what happens, then report back.

David Goddard · Post by **David Goddard** » 04 Nov 2003, 01:41

Some data. The interior temp sensor RTD has a resistance of about 12,000 Ohms at 20 deg.C (the grey wires on the 4 pin connector.

Hold the RTD between your fingers at it drops to about 7,000 Ohms.

Richard Gallagher · Post by **Richard Gallagher** » 04 Nov 2003, 02:33

Thanks for that Dave I'm intending to get the sensor out tomorrow.

Richard Gallagher · Post by **Richard Gallagher** » 07 Nov 2003, 02:15

I had a look at the car tonight and would you believe it but the air con system is different on them despite them both being relatively late MK 1's. On the problem one (RP 7518) the A/C ECU is fitted to the right of the pollen filter, whereas the other one (RP 7179) just has a hole in that place with wires disappearing behind the dash. So it won't be quite as easy as I hoped to swop the ecu's. Like-wise the pollen filter on the earlier one is secured with screws compared with a slide fit on the other.
Still at the weekend I will swop the temp sensors and see what I can find.