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-   -   '87 300E rear power window inoperative (http://www.peachparts.com/shopforum/tech-help/7723-87-300e-rear-power-window-inoperative.html)

vetz 05-31-2000 10:12 PM

The driver side rear window will only go up but not down when using the rear switch. The front switch does nothing. I've taken everything apart and both switches and the motor are fine. I don't have the cd wiring diagram. Can you tell me which wire(s)is defective? Thanks

jeffsr 05-31-2000 10:35 PM

The down wire is defective.. :D :D. Seriously, how did you determine the switches were OK?? I am not sure, but I think these switches are series/parallel wired which means that both have to be intact for the windows to work. I'll have to check that. However, all the switches do is reverse the polarity of the current going to the motor for up and down function. If the front switch is dead and you've tried a known good switch there, and this failure occured suddenly. (did it??)then start at the console and check voltages for the center conductors for that switch. Should show 12 volts with key on. If no juice, then the problem is further downstream. if you've got the 12v, then it's a crappy switch.

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Jeff L
1987 300e
1989 300e
1987 BMW 325

J.HIDALGO 06-01-2000 12:01 PM

I had problems with both of my rear windows at different times. I tried cleaning the switches with contact cleaner but, it did not work for me. In one of them, after checking voltages, I found that the wires between the door and the frame were broken.In the other one, the motor was gone. Not too hard to do yourself once you have the door cover off.
J.H.
86 300E

jeffsr 06-01-2000 01:19 PM

I checked the wiring schematic. Those switches are wired series/parallel. Therefore, if the front one is shot or partially shot, you will get the symptoms you describe. Start checking in front. The feed current for the window starts there.. Good luck...

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Jeff L
1987 300e
1989 300e
1987 BMW 325


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