C3 Aircross 2018 - heated seat failure

Faults and Technical chat for the Citroen Aircross
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Joined: Thu Mar 07, 2024 1:06 pm

Post by cafebabe@gazeta.pl »

Hello, Forum!

So, I have a problem with seats heating (C3 Aircross 1.2 MR'17 Shine). Passenger side works OK, on the driver side - it's cold.
As I understand, both are guarded by single fuse, so blown fuse can be ruled out I guess.
The LED in the adjustment wheel turns on on both sides a few moments after engine starts up.
I've measured resistances on the (unplugged) plug for sitting part (4 pin green), it's around 10Ω between pin 1 and 4 (thicker wires, heating circuit itself?) and around 10kΩ between pins 2 and 3 (thermoresistor?), while on the passenger side the 1-4 resistance is much lower, like 1.4Ω.
When running, both seats have 2.5-3V between pins 2-3. As for 1-4 there is around 5V for working passenger side and 0V (with some short glitches when switching heating levels) for driver side.
That would mean the control module is not providing the necessary power to the driver seat heating, while still sensing its temperature? Can this be caused by too big resistance or is there some other failure possibility?

Update: while the knobs for heating power selection are not interchangable, the circuit boards are. After swapping those, it's the same - so failed SMD resistors there can be also ruled out I think.

Best Regards!

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