Xm V2 Seat Heating, Only one seat works, others are cold

Gentlemen, I am new to this esteemed forum and my first post regards my 1997 XM V6 Exclusive. Namely, I have discovered that the seat heating does not function on all but driver's seat. I checked the fuses and they're OK. I disassembled the front passenger seat and found two connectors leading to the seat (5 + 2 leads) which is attached to the regulator which further leads to the heating rheostat control.
Any suggestions for the possible cause and anybody knows the wiring for the seat? Thank you in advance.

Hi John

1997 V6 Exclusive is right on the cusp of the change from the 12v to 24v. Which do you have? The seat heating on my previous 1996 V6 Exclusive seemed to be different to my present 2000 V6 Exclusive (the 2000 Exclusive has heated rear seats and the whole seat heats up rather than just the base - plus they are really quick to heat). The seats on eariler exclusives seemed to be more fragile than later ones mainly due to the heating element circuits which can break, effectively stopping them working, especially if someone stands on them. In order to fix them you have to take off the seat cover and take apart the element from the seat stuffing, then replace the element. Apparently it's tough to do and make it look like a good job.

Cheers

Tony

Thank you for your response. Mine is 12V. You are, actually suggesting that the heater in the seat is broken. This sounds controversial because the heating only works on the driver's seat which is the most often used, whereas back seats, hardly ever used, are out of order. Does anyone have the wiring diagram for the two connectors coming out of the seat? Thank you again.

This post has been edited by John Malkovich on February 19, 2008 12:54 pm

Think about it......where does the driver often place heavy boxes and where do kids normally jump around in cars ??

Hi John M

The earlier exclusives with heated seats have an individual controller box on each of the four seats. The controller boxes are fixed to the frame under the front seats and behind the side squabs on the rear seats. The controller boxes just accept the signals from the 4 position switch for each seat for the different heat levels and off. Fusing is usually seperate for front and back seats. Seat back heating and seat base heating are wired in parallel so only the faulty one should stop working. The failure mode is normally heating wire breakage where it is wrapped around the stiffening wires that hold the fabric/leather in the deep upholstery creases. Mk2 seat heaters are fortunately on a seperate piece of fabric once you have the seat covers off. (Mk1's are glued to the foam seat cushions making repair very difficult).
First it might be worth checking out the control switches from the 3 non working seats by trying them in place of the working one. These switches do sometimes go faulty and were not available from Citroen when I asked about 3 years ago. You mentioned the front seat wiring as 5 + 2. I recognise this as a non heated seat wiring. The 2 wire orange plug is the explosive seat belt device that is best left untouched unless the battery has been disconnected and left for 10 mins. The other 9 pin Black Plug has all wires populated on heated seats but only 4 wires on non heated seats. Similarly the next wiring loom back in the circuit Citroen supplied in both heated seat form with all 9 wires and nominally VSX type with only 4 wires present. I have come across a few XM's with swapped seats/incompleat wiring where one car has suffered to enable another one to have its spec changed.

Regards

XMexc

XMexclusive,

I was referring to the seat base only which has two connectors (correction, it's 4 pin and 2 pin connectors, the latter with two black wires). I had already checked fuses, 4 position switch, as well as transistor regulator in the black box underneath the seat and they are fine. I would test to conductivity of the heating element in the base but don't know the wiring pattern of the 4 pin connector.

Hi John M

Will look out a seat wiring loom and report back.

Regards

XMexc

Hi John M

The 4pin & 2 pin brown plugs have the contacts numbered on both the plugs and sockets. There are 2 heating elements in each seat but only one of the heating elements has a temperature sensor for heat achieved feedback to the control box. On the front seats the feedback sensor is in the seat base cushion. On the back seats the feedback sensor is in the seat back cushion. For each seat the heating elements are actually wired in series. Despite the difference in heat sensor position all the wiring seems common for all the seats. The 4 pin plugs come from the temperature regulation control unit. Contact 1 of the 4 pin plug always goes to contact 1 of the 2 pin plug to feed the first of the heating elements. The other 2 pin plug pin simply chains the 2 heating elements together. Contact 4 of the 4 pin plug is the return from the chained heating elements. Contacts 2 & 3 of the 4 pin plug are the temperature sensor connections.
So if you measure the resistance across pins 1 & 4 of the four 4 pin plugs you should see about 2 ohms if the two heating elements are ok. If you get an open circuit then check the resistance between the 2 pins of the 2 pin plugs. If that heating element is ok you should see about 1 ohm on the meter. To test the other element in the pair check pin 2 of the 2pin to pin 4 of the 4 pin.
I do not know about testing the temperature sensor but think I have a stripped out heated front seat somewhere as I took one to bits to send the cover to On-the-cut a while ago. I will see if I can find it.

Regards

XMexc

Thank you so much. I will post my findings.