Outside Temperature Readout

[kiwi]

Hello all,

It is winter here but the temperature readout in the RH Display (in my S1 2.0sei) has for some reason decided it is summer. It has become very optimistic and reads between 30 and 41c - even when driving through snow. Has anyone else had this to contend with? Grateful for any pointers on where to start. I'm hoping it isn't the display thats at fault.

Regards,
Kiwi

[colinxm]

Hi Kiwi, It won't be the display, it's certainly the small temp sensor that lives in one of the rearview mirrors - probably the LH one, just look underneath for a small, round protrusion in the mirror housing and that'll be it. You'll need to remove the mirror glass to get at it. New ones can be obtained from Citroen very cheaply but you'll need to cut out the old and solder in the new as it's built into the loom - not too bad a job, will take around one hour the first time you do it.

Good luck, Colin.P

[Peter.N.]

Hi Kiwi

Mine is doing the same. I have already changed the sensor and the display. If I disconnect the plug from the car to the door it then reads -C which is what normally happens when the sensor has gone o/c. I have tried two new sensors, so am pretty sure that's not the problem. There is obviously a low resistance across the sensor, I can only think that water has got into the connector inside the door. I havn't had the necessary adrenaline surge to take the panel off yet, if I find it befor you I will let you know, and I trust, vice versa.

Peter.N.

[colinxm]

Hi Peter, I haven't actually had that problem myself, I got the same as Kiwi when the display would be wildly optimistic. I have found new sensors from Citroen to be the only cure, they seem to have a limited life expectancy so I've done 3 in total now plus a couple for new found friends (they magically appear on my doorstep when their xm's break).

Regards, Colin.P

[xmexclusive]

Hi All

I am afraid Citroen made a few changes to both the temperature sensor itself and its position during the XM production.
In early cars it is fixed by screwing to the side of one of the air vents in the front bumper. Then it moved to pushing into a hole in the underside of the Mk1 and early Mk2 passenger side mirror shell. On later (most) Mk2 cars it then moved to the underside of the mirror hinge held in place by a clip in black plastic panel (often missing so can be seen dangling or cable tied out of the way) with a hole for the sensor bulb. During these changes the little black sensor block got progressively smaller so the older ones do not fit in the newer cars. With Mk2 cars the mirror shells still have the sensor holes/fitting position as well as the one on the underside of the hinge. Threading the wires through the Mk2 hinge to use the alternative position is not easy. On LHD cars the sensor side swaps and is still on the passenger side. This is simply because all the drivers side wires in the door connector are used for other functions.
Surprisingly I have never come across a dead sensor but quite a number that have wiring problems following replacement as the normal method is to cut the wires before they go into the door from the mirror and crimp or solder the new sensor on. Over time these connection seem to go high resistance as can the 2 pin connector behind the door panel and the contacts in the door to chassis plug.
High temperature readings could be a defective sensor but are just as likely to be due to high resistance connections.

Regards

XMexc

This post has been edited by xmexclusive on July 25, 2007 12:00 pm

[kiwi]

Thanks all for the info. I've got a spare weekend coming up soon so will have a go at finding the sensor. The passenger window is painfully slow so I might even take the door panel off to have a look in there as well. Can the mirror assembly be swapped out without pulling the door apart or is that wishful thinking?

Regards,
Kiwi

PS: Have just seen the UK floods on the news - hope no club members are affected.

[Peter.N.]

It could be of course that I have had two duff sensors, I think I will just try disconnecting mine at the mirror, where I just cut the old leads and soldered and sleeved the new ones, before I take the door panel off. I have had many of these sensors fail, and they, so far, have all gone open circuit i.e. reading in minus C and flashing, but mine is exhibiting low resistance symptoms - reading high. I will try and do it today if it stops raining for five minutes, and report back.

Peter.N.

[xmexclusive]

Hi Kiwi

The mirror is held on the door with 2 screws that can be seen just above the top front corner of the trim panel. There is a third spigot into the the door at the other corner of the mirror bracket but this is just push fit. The mirror wiring runs in a rubber sleeve into the door frame at the centre of the 3 fixing holes. If you remove the door trim panel you will find up to 5 connecting plugs clipped to the door frame. From memory these are Red, White (male & female) Brown and Yellow. The new sensor can be plugged in here for testing purposes (I used a hair dryer and an ice cube). The Brown 2 pin connector is the temperature sensor one.

Regards

XMexc

[DerekW]

"The new sensor can be plugged in here for testing purposes (I used a hair dryer and an ice cube)"?

Ah! Shrink the pin and enlarge the socket? Clever.

Derek

[Peter.N.]

Hi All

I have just got round to checking my sensor, and I think I must be going senile! I distinctly remember changing the sensor twice and taking the first one back to Citroen as faulty, and again, they wouldn't change it the second time so I had to buy another, in fact the first one was still in the glove box, with short, soldered and sleeved leads where I had fitted it. When I removed the cover from the bottom of the mirror and pulled the sensor out, it was the original one, the leads had never been cut! . The only possibel conclusion I can come to is that I changed the mirror - but I don't remember doing it.

Anyway, to the information that may interest you. The good sensor reads about 2k ohms at about 25C, the one I took out only read about 1k and was giving a reading of around 45C, having replaced it I now have a sensible reading of 30C which was probably about right with the sun shining on it. Usually when these fail they go open circuit, reading ---C, but this one had gone low resistance, causing it to read high.

Peter.N.

[Assich]

Yep when mine failed it was reading high too.