Posted October 1, 2008 (edited)


Try the following to diagnose the problem:Since your passenger's side seat heater is working fine, the first (also costs no $$) place to start is by swapping the passenger's side switch into where the driver's side switch is now connected and see if that resolves the problem.The switches can just be pried up carefully and then connected after the swap.If that doesn't resolve the problem, then you can do the same thing with your seat heater relays, which are under the seat bottoms.The relays are located near the outboard sides of the seat bottoms, about halfway between the front and the rear of the seat bottoms. The relays are black, about 2 inches tall by 1 inch by 1 inch and have the part # 996 618 521 00 stamped in white lettering on them.Until you determine your relay is bad, there is no need to remove the driver's side relay from its mounting point, where it is attached to the seat frame by a black plastic rivet.Start with the passenger's seat. The seats can be unbolted from the car's floor by unscrewing the four bolts that hold it in place. Two bolts in front (one on each rail) and two bolts at the back. They are torx bolts, but you can use a fine 10mm (1/4" drive) socket to remove the bolts. There is no need to take the seats out completely. (Although it is possible to take the seats out and put them down right next to the door sills while they are still connected, it's unwieldy, you need a lot of room to have the two doors wide open and you run the risk of scratching your door sills, etc.)Just undo the four bolts and lean each seat back. Stick a small block of wood under the inboard side (closest to the center console) of the seat bottom at the front and you will be able to easily access the black plastic rivet that holds the metal bracket that is pressed into the side of the relay onto the seat frame. Now push the plastic pin in the middle of the plastic rivet towards the seat cushion and it (the pin) will fall into the foam rubber. You can then retrieve it and re-use it.Here is a photo with the seat heater relay highlighted in blue:Here is a closeup of the relay:The advantage of not taking the seats completely out is that you don't have to disconnect the main connector under the seats and thus eliminate the possibility of setting off your airbag light. If you want to take the seats out, make sure that the ignition is off and the key is out of the ignition and don't turn it back on until you have completely re-assembled everything.Once you remove the relay from under the passenger's seat, go to the driver's side and merely unplug the connector that is plugged into that relay and just swap the relays (i.e., at this point there will be no relay under the passenger's seat and two relays under the driver's seat, with the original passenger's seat relay connected there and dangling, and the original driver's seat relay disconnected but still mounted on the seat rail.One last point, the relays themselves are identical between the passenger's side and the driver's side. The small metal bracket that is pressed into the side of the relay housing is the only slight difference. That bracket is mounted as a mirror image to itself (on the two housings) between the passenger's and the driver's side.The switches fail less often than the relays, so my money is on a faulty relay.Let us know what you find.
Courtesy of RennTech