C5 : BABY IT's HOT OUTSIDE !!

johnway · Unread post by **johnway** » 15 Jan 2009, 17:07

Hi Folks,
It has been quite a while since I have had to post anything (the C5 has been behaving itself beautifully), but now a strange quirk has developed : exterior temperature reading is a balmy 90 degrees!! I know we are facing global warming, but that reading is ridiculous. I tried the usual cure for electrical gremlins i.e. disconnect battery and let everything reset but in this case nothing doing. All ideas/suggestions very welcome. Regards, John. 8)

Unread post by **myglaren** » 15 Jan 2009, 17:23

My first guess would be a defective thermistor in the mirror.
Apparently easy to do if you can handle a soldering iron and can dismantle the mirror without breaking it.
A new thermistor is approximately £14 from the dealer.
Dismantle the mirror before you buy the thermistor, just in case you break the glass.

johnway · Unread post by **johnway** » 15 Jan 2009, 17:32

Hi Steve,
Thanks for your 1st guess - I have read something similar elsewhere on another topic so you may well be correct. However, before I break anything or buy anything I am hoping somebody out there has experienced the same malady with their C5 and cured it. Thanks again, Regards, John.

civvie · Unread post by **civvie** » 15 Jan 2009, 18:44

I had the same problem a couple of years ago, mine read the other end of the scale IE it shows about 3oc. The dealer changed the sensor under warrenty and said it would have to be replaced as it would give the computer incorrect readings, so I assume the car would think it is just above freezing and change the mixture to match.

Steve

wheeler · Unread post by **wheeler** » 15 Jan 2009, 18:49

99% certain it will be the temp sensor in the n/s door mirror. It can affect the operation of the air conditioning system if its reading incorrectly.

Mandrake · Unread post by **Mandrake** » 15 Jan 2009, 22:27

wheeler wrote:99% certain it will be the temp sensor in the n/s door mirror. It can affect the operation of the air conditioning system if its reading incorrectly.

Interesting.

Does anyone know if the outside temperature sensor in the door mirror on a Xantia is also used as an input to the air conditioning system ?

My sensor has become intermittent and sometimes the reading heads well into the negatives and then to a blank reading, usually restored by slamming the door closed

but lately it's getting more troublesome.

Is it difficult to get at the sensor and the wiring ? I presume the mirror glass has to be removed from the shroud somehow, any tips ? I can deal with the spider who lives behind the glass at the same time.

Regards,
Simon

arkweld · Unread post by **arkweld** » 15 Jan 2009, 22:53

The glass does'nt need taken off , underside of the mirror fitting there's a clip that removes . The sensor sit's on the clip poking down from the fitting . If there's enough slack wire to work with you can solder from there .
Or ultimately , it's a door card removal to get to the tail-end connection "

wheeler · Unread post by **wheeler** » 16 Jan 2009, 07:42

I dont know if you meant the Xantia or not but I cant see how you could change the sensor on a C5 without removing the glass, not without damaging the mirror housing anyway. I't fairly easy to remove the glass anyway, just flick of the metal circlip with a thin bladed screwdriver.
Im not sure if the exterior temp sensor has any effect on the A/C system on the xantia.

Unread post by **CitroJim** » 16 Jan 2009, 07:49

wheeler wrote: Im not sure if the exterior temp sensor has any effect on the A/C system on the xantia.

I don't believe it does. As far as I can tell, it simply drives the temperature display. I base that on the observation that if the sensor is not working it makes no difference to the performamce of the heater and secondly, the lower spec. A/C equipped Xantias did not have outside temperature sensors or displays.

The outside air temperature in a Xantia, for A/C purposes, is measured on a sensor just downwind of the heater box air intake.