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Discussion Starter #1 (Edited)
Been lurking for a while. Thought I would register and post this, since it might help out someone else.

I bought a 1987 300E over a year ago. Has around 97,000 miles on it. Yesterday my wife drove it to pick up a take out order at a restaurant. She rolled down the driver's window at some point. Because when she returned and pulled into the garage, she told me that the window would not go up.

Upon examination by yours truly, NONE of the windows would now go up or down. And the driver's side window was down. She's hard on machinery. She could tear up an anvil.

There are many threads on here about window problems. Solutions offered are:
  • Check fuses: No problems with my fuses
  • Disconnect battery for a while: Did that, but didn't fix it
  • Turn key in driver's side door to lock and hold it: This trick only works for years sometimes after 1987.
  • And many suggestions about checking window switches, wiring and window regulators: This might be it if only one or two windows are acting up. But probably not when all 4 windows are suddenly not working
I finally discovered that there is a power windows relay in the relay compartment behind the fuse box. That sounded like a good suspect.

Here is how you get to it on a 1987 300E. Unclip the top of the fuse box and lift up to remove it. There is no clip for the relay compartment behind it. You have to use a Phillips screwdriver to remove the 3 screws along the left and right frame (6 screws in total) to separate the frame surrounding the fuse and covering the relay compartment. Then lift it up where you can now get to the relays.

The power windows relay is in the middle row farthest to the back, up under the cowl. Yeah, the problem is always the one in the most inconvenient spot...

You can't really get to it with your fingers. I used tongs to reach back there, applied pressure on the sides of the relay, and lifted it up. Finally, it came loose.

I noticed there was a little corrosion on the prongs. I used a q-tip and some cleaner to try to clean the prongs and where the relay plugs in. Then I put in back in its proper place, thinking that might do the trick.

Turned the key in the ignition, pressed the window switch, and now all the windows work. Mission accomplished. So if none of your window switches work and the fuses are good, you might as well check that power windows relay next. It worked for me.

Now there are 10 or so relays in that box, for a variety of electrical functions. Some of them seem to be the exact same part. For example, the same part number is plugged into both the power windows relay slot and the power seats relay slot. So if my power windows relay would not have worked after cleaning it, I could have just unplugged the power seats relay and put it in the power windows slot. Then my power windows would have worked, but not the seats.

If no windows worked and one or more were down, and you were caught in a rainstorm or it was a security risk to have to park it, then switching out the relays might be the best emergency option.

I ordered a spare relay to keep in the glove compartment. The price is about $40. And it would be a good idea to keep either some tongs or maybe needle nose pliers in your toolbag in the trunk to be able to extract it. Trying to wedge a flat head screwdriver back there under it and prying it up might do some damage. Tongs work well.

It took me about 30 minutes or so to take the top off the relay box, remove the power windows relay, clean the prongs and put it back in. Anyway, if none of your windows work on an early W124 (and your fuses are good), and you start frantically doing Google searches to find possible solutions, then maybe this will help.

1989 300CE & 1971 280SE; 73.5 911T
172 Posts
On my '89 300CE the driver's window wasn't moving when I pressed the window switch.
I replaced all the original fuses with copper/ceramic fuses. The contacts all looked clean.

I was contemplating what was involved in replacing the window switch, the relay or the in-door motor- none of which was a very appealing operation.
Just happened that MercedesSource posted a video about fused electrics not working. Kent demonstrated rotating a fuse in its socket to fix an issue.

So, I tried twisting the new left front window fuse in its socket.
That's all it took to "fix" the window problem, now it works every time.
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