"olddog" <olddog@newtrox.com> haute in die Tasten:

I have made similar experiences with my `94 Xantia VSX. The car has
an automatic temperature control, which means that you choose the
desired interior temperature with a switch (between 17°C and 27°C),
the french electrobox does the rest, adjusting heating temperature
and fan speed. If it is warmer outsides than you want to have it
insides, you can switch on the Air condition with an additional
switch. So far so good.

I have found out that this system works better when it is sunny and
hot outsides than on cold, wet, dark days. During winter I found that
the heating system produced warm air after just half a mile of
driving, but very often it stops heating when there are 18°C inside
te car - very unpleasant.

I was able to track down one fault: There is a temperature sensor
built inside the dashboard, just near the clock. This sensor is about
the size of a cigarette lighter, and it has a small electric motor
and a fan. This fan is bound to produce a constant airflow around the
temperature sensor itself (the sensor seems to be a temperature
regulated resistor). The whole sensor unit has four wires, two grey
wires, one black, one red. I assume that two wires power the small
fan, while the other two wires connect the sensor to the heating
system. I have found out, that this fan does not work most of the
time. If I drive the car 30 days, the fan may run on one or two days.
I have also found out that the whole unit gets warm when the fan does
not run. Maybe something is blocking the fan (although I have not
found any sign for that).

If the fan does not transport fresh air to the sensor and if the
sensor unit gets warm, the sensor will probably read a false, too
high temperature - and it will switch off the heating:-(

I have found out some kind of strange workaround. I have pulled the
sensor out of the dashboard and fixed it to one of the vent air
nozzles (the right one of the two central nozzles just above the
radio). Now I can force the ventilation of the sensor by simply open
or close the nozzle. This does affect directly the ability of the
system to regulate itself by itself, so it requires some manual
regulations. Up to now this workaround works quite well, I was able
to maintain a sufficient temperature in the car. I don't know how
this will work in the winter time.

Why didn't I just change the sensor? First of all, I am lazy and
greedy. These sensors are for sure handmade by a bunch of
aerospatiale engineers in their spare time between two Ariane rocket
launches, so they will cost a fortune. Besides that I cannot reach
the wiring plugs without taking apart the whole dashboard - I'd like
to avoid that. Second reason: I am not entirely sure, wether the
faulty sensor is the only reason for the errative heating. If I were,
I'd be more enthusiastic about getting the sensor done.

I have heard about problems with this sensor and the fan in Xantia
and XM. Maybe this can be helpful for the C5 also.

Frank  

Thanks guys, your problems are all very interesting , but i'd rather hear
from someone whou might know the answers. Where are you Adrian ? Cheers. Ray

Hi!

I guess that outside temp. sensor is faulty or has some contact problems.
It is located under co-driver's mirror.
Been there, done that...

cheers,
make