[thereza]

When I turn on the driver side heated seat, the lights turn on for about a second then turn off. I can hear the relays switch on/off when this happens. The passenger side works fine, so it's not the fuse. I've found a number of cases of this on the forum but no consistent issue.

I want to check the resistance of the heating pads as well as test the temperature sensor. However, I've not been able to find details as to where these parts are in the car. I have the bently manual but can't find the relevant electrical circuit in the book (not sure what section to look under / haven't found it so far). I found the relevant fuse but there are no details on that page. It references A187a driver seat heating module but I'm not sure how to find the details of that module (i.e. what page/section to look for).

I'm going to hook up the scan tool tomorrow to see if it threw any codes.

Any pointers would be greatly appreciated.

[smass]

They don't share the same fuse. Also, drivers side is turned on by the CAN bus. Pass side is turned on by a relay. Scanning for codes is probably a good 2nd test after checking the drivers side fuse.

[thereza]

Originally Posted by smass

They don't share the same fuse. Also, drivers side is turned on by the CAN bus. Pass side is turned on by a relay. Scanning for codes is probably a good 2nd test after checking the drivers side fuse.

Sorry for the giant image below.. (side question, what does the X##### numbers mean in the image, and how can I find an expanded view of A187a?)



Looks like they share the same fuse here, and I've read as much online. Also, you can hear an audible click from the module, so I'm guessing it has power.

It doesn't look too insane to take the seat out which I might do. According to the TIS, there is an extension cable you can use to test the seat outside the car -- but I've not been able to find a place to purchase it. Will investigate further..

[thereza]

I spent hours digging up all sorts of technical info, but when I went to check it out, it seemed to work fine today. 😓

[AlpineBoost]

My '09 has the exact same issue as yours. I intially did some research on it, iirc people were saying it's probably the element, but that's as far as I went with it. I've just been living with it like that for about 2 years. Once every few months I'll press the button just for the hell of it to see if it magically works again. Never does. I'll probably replace both seats with non-heated aftermarket seats sometime soon anyway.

I realize that my story is an unhelpful one

[smass]

Sorry. Just noticed you have a coupe. My comments were for a sedan. I forgot coupes use seat modules/can bus activation for both seat heaters.

[pedro2u]

I successfully did the same seat swap in my 2008 e92 335xi. Read this thread:

https://www.e90post.com/forums/showthread.php?t=1746729

[Kenneykickin]

I have the exact same issue.. happened after my ecu got bricked/electrical problems started happening after that. But this is happening in passenger side the driver side works fine. Had to get ecu unbricked and cas had to be re done to be able to get the car to start but never fixed my heated seats and my Speedo cluster randomly will go to the 0 mph like it’s resetting or something. And my parking brake light warning comes on from time to time now when it’s not engaged.

Bought car in 2015 and still has the battery the dealer replaced it with before I bought it. 7 years ago.. maybe the battery was never re registered after the ecu and cas got messed up? No signs of battery failure yet but it’s old I should either replace soon or least make sure mine is properly registered after the fiasco that happened. Who knows if mechanic ever re programmed everything they were suppose too other than ecu and cas cause my end goal was to get the car running again. Could have got it running than kicked it out to me without properly re doing everything