Heated seat not working

[Jay 535i]

Driver's side is fine, but no action at all on the passenger's side. Pressing the rocker switch in either direction causes the light to go out rather than become brighter. Any tips? My wife's bum is cold.

[Scott H]

1) Fuse under rear seat (unlikely since the seat works and the switch is lit)
2) Switch has gone bad (~$30 from BMA)
3) Heating elements are shorting out. This can happen from moisture corroding the element coils.

As usual, start from cheapest.

Also know that the switch is different on later cars.....make sure you get an early one.

Also check to make sure all of your wiring harnesses are securely plugged in under the seat.

Driver's side is fine, but no action at all on the passenger's side. Pressing the rocker switch in either direction causes the light to go out rather than become brighter. Any tips? My wife's bum is cold.

[rreimund]

good stuff.. I've got the exact same problem.. None of the heater settings work, but the switch lights up with the headlights, and when you turn the rocker switch "on" the illumination goes out when it should get brighter..

Looks like I'll be checking fuses (again), harnesses and getting a new switch..

[Jay 535i]

Thanks!

I take it a bad switch is a pretty common occurence, and the most likely culprit? I'll get one from BMA.

[Alan_525i]

Also do note that her seatbelt must be buckled for them to work. Possible that the sensor in there isn't working. Kind of BMWs encouragement to be safe.

[Jay 535i]

Also do note that her seatbelt must be buckled for them to work. Possible that the sensor in there isn't working. Kind of BMWs encouragement to be safe.

Really!? That's very interesting. Any way to test that sensor?

Strange 'feature'...

[Scott H]

There are seat occupancy sensors in later cars which help with determining airbag deployment, etc.

There is a sensor in the seat belt clasp but it has never needed to be connected to have the seat heater work in my 1989 535 or my 1991 M5. I'm pretty sure Alan is mistaken at least when it comes to the E34

Really!? That's very interesting. Any way to test that sensor?

Strange 'feature'...

[Qube]

That's EXACTLY the problem I have too. I posted somewhere in another thread (not a fix).

[Jay 535i]

That's EXACTLY the problem I have too. I posted somewhere in another thread (not a fix).

Okay, there should be enough of us to figure this out...

I'll get a new switch and see what happens.

[Qube]

No kidding.

I'll check the wiring loom under the seat tomorrow when it's drier. In the mean time, I need to see why the driver side only goes on maximum heat setting.