1994 Merc E320 window issue.
 

The windows in my 94 Merc e320 work intermittently. They all work or they all don’t work. They have been not working for about 2 weeks but worked for about 2 weeks prior. This has been going on for months.
The fuses are new, I swapped out electrical box under left rear seat with my parts car that the windows work. The wiring going into fuse panel feel secure and clean. It has 2 fuses which makes me think there are 2 circuits. Why both would stop working, I haven’t the foggiest. Anyways, I got the engine light to turn off, the ERS light (swapped airbags) and this is the last thing to fix.
Any suggestions? I have a parts car where the windows work so I can swap stuff.
Thanks.

If its pre 96, I'd inspect the harness going to the comfort module carefully. Could be bad insulation causing a short.

Comfort module under rear left seat?
I’m thinking ground somewhere.
Sorry, 1994.

Not a current 124 owner, but I believe its under rear passenger side seat. But yeah, that box. In MB terminology, they call the relay box for the windows/sunroof the comfort/convenience module.
Could be a ground, yeah, but I'd inspect the harnesses carefully. Its usually the underhood stuff that fails, but it all has biodegradable insulation.

There are a bunch of troubleshooting threads if you google w124 comfort module. Does the sunroof work when the windows don't?
There's also a feature that closes all windows and sunroof if you lock doors with key and hold it in the lock position for 3 seconds or so. Does that work?

That’s amazing. I turn the key and all the windows went up. I turn and hold the other direction, all go down. Doesn’t fix my problem but can get me out of a bind. Thank you.

Ok. So apparently there are two power sources to the c/c module, one goes thru the locks, the other not. Dig around in the google fu for w124 comfort module, there's some stuff from a british mb site discussing this.

I did notice the wire that came from one of the window fuses goes to the c/c module.
Thsnks