If the power windows and sunroof on your BMW E36 suddenly stop working, there are a few things to check.
First, check the Child Protection Control–that’s the mysterious button behind the right side of the steering wheel. It’s actually a circuit breaker that is designed to trip when little Johnny tries to close the power window on the dog’s neck. If it’s popped out (you’ll see a red outline), push it back in.
Then, check the fuse in the main fuse box. It’s under the hood on the driver’s side.
If both of those are OK, suspect the Comfort Relay. That’s the main relay that provides power to the windows and sunroof. The relay is located in the Auxiliary Relay Panel, which is next to the steering column under the driver’s side dashboard. In the BMW 3 Series Service Manual (1992-98), the Aux Relay Panel is described on pg. 610-2, and a schematic for the power windows (1993 325i) is on pg. ELE-233.
Roadfly also has a good writeup about the Comfort Relay here.
Update June 14 2007: RoadFly used to have a good article there. The article seems to have been KIA by the corporate sell-out. Fortunately, the Wayback Machine still has copies of the original article. Unfortunately, some of the original photos are missing.
Update June 15 2007: There are a number of posts on RoadFly’s bulletin board regarding the Comfort Relay. Running a search there may turn up something useful.
Update Nov 20 2007: Here’s an interesting article on the E36 comfort relay from UnofficialBMW which may be helpful.
This seems to be my most popular post (such as it is), so I’ve enabled comments in case anyone out there wants to get a useful discussion going.
All I can say is ” thankyou thankyou thankyou thankyou …..thankyou ” a million times. I had a temp in who was looking for work and gave them my BMW to clean and polish, and the rest is obvious in hindsight. I ‘d checked all the fuses, relays, started stripping down the wiring. Again..
Thankyou
Bruce
Southern part of Darkest Africa
which is the voltage among the points 8 and 9 of the relay comfort, when the door this open one and when the door this closed?
First, let me mention that I’m not a mechanic nor an electrical engineer, so what I’m about to say could be total baloney.
I assume you’re talking about a ‘93 sedan. Looking at the Service Manual, p. ELE-227 describes the Power Door Locks for 1993. There, you’ll find the Central Locking Module (also known as ZVM). Pin 9 from the ZVM goes to Pin 9 on the Comfort Relay with a violet/yellow wire (p. ELE-233). Pin 8 on the Comfort Relay is ground, with a brown wire.
I’m assuming the ZVM is some sort of computer; thus, the Service Manual doesn’t list schematics or behavior of Pin 9. However, Pin 9 on the Comfort Relay (the input from the ZVM) goes to a transistor, which then controls the relay itself. Thus, I would guess that Pin 9 should be high when a door is closed, and low when a door is open. Of course, Germans being Germans, who knows?
In any case, if the voltage on Pin 9 does not change when you open or close the door, then the ZVM is probably doing something funny.
Update: Of course, that would be the behavior once the car has been turned off — the windows will continue to operate until one of the doors is opened. When the car is actually turned on or running, I would expect Pin 9 to be high regardless of the doors, since the windows are supposed to operate any time the car is on/running.