Heated Seat And Tail Light Problem - BMW Forum - BimmerWerkz.com

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post #1 of 2 (permalink) Old 03-17-2005, 11:54 AM Thread Starter
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I have read everything I can about the heated seats problem. I have found 3 known issues
1. Switch doesn't work
2. Wiring or fuse problem
3. Heating elements are bad

Here is what is going on with mine. The switch works fine. The passenger seat works fine. I looked at the fuses and they all look fine, but if anyone has a fuse diagram(1997 M3) that they could send me it would be helpful seeing as I can't figure out what fuse is where.

I just checked the wiring and there are 3 wire connector to the seat. There are two small ones and one big one with two plugs in it. I used a omhmeter and checked the big one and it is getting voltage, but I don't know if that is the right one. I think if it is getting voltage then the heating element in the seat is shot. I have two pictures of the wiring harness and wondering if anyone can tell which one is the heated seat wires.

Second problem is I am getting a brake light error on the computer. It only comes on from time to time and as soon as I shut the car off it goes away. Here is a pic of the tail lights with the headlights off. Are all the correct lights coming on with the head lights off? used
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2002 Bmw X5 4.4I
1997 Bmw M3 3.2L
1988 Sunbird Eurosport SLC 5.7L
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post #2 of 2 (permalink) Old 03-17-2005, 08:54 PM
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from the pictures and if memory serves i think the first connector is for the heated seat. it probablly is a bad seat heater mat. one way to somewhat check would be to check the resistance of the mat. if it doesn't show a resitance like it is open then that is your problem, however it will show more resistance than just plain wire or a relay etc... becasue the heater mat is nothing more than a bunch of resistors. and i don't know what the spec is for the resistance. but if the fuse is good and the switch is good there is really nothing else other than the actual wiring from the switch to the seat that could fail.

as for the brake lights. you probablly need new light bulb sockets and maybe new rear tail lights. it is really common for the E36 to have the sockets not make good enough contact on the tail light assys. and arc from socket to tail light and cause the metal to get corroded and sometimes burn holes in the circut of the tail light. just take out all your light bulbs and first make sure that none of the bulbs are just beginning to burn out and maybe the philiment in the bulb is making temporary contact. then when you have the sockets out check for any black marks on the contacts where the sockets make contact with the tail lights. also check the tail light assys. for the same thing. if you have holes burned through the contacts on the tail lights you can fix them but it isn't a garaunteed fix but it could work. what you do is clean the area where the arcing has burned the hole. then get a soldering iron and heat up the metal on the tail light then put a drop of solder on the tail light and file it down untill it is nice and smooth so it will make good connection. however if your sockets are black and nasty from the arcing it is just easier to replace them.

does the check control actually say brake light error or does it say brake light circut? if it says brake light circut it is probablly a brake light switch.
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