Another W124 Rear window thread
 

So I've spent some hours researching (several reliable Benz forums) and testing with a mulitmeter. Perhaps my answer is already out there but I could not find it.

Here are the facts:

1. W124 UK RHD 300TD Estate (non-turbo wagon) auto transmission, owned by me since June 2015.
2. As of today, window switches all operate with the KEY OUT OF THE IGNITION. That's a new one on me.
3. Laser line alarm removed many moons ago as it was causing all kinds of problems.
4. Console switches test ok and I can hear the convenience relay clicking when I engage the switches for the rear windows
5. Driver's (starboard side) rear window:
-no broken wires in door: I checked
-console switch engages convenience relay
-it used to go up and down, then eventually was failing intermittently, now not at all
6. Passenger (port side) rear window:
-motor engages with console switch, not door switch.
-probably regulator or something else broken/dislodged (but that is a separate issue from the power issue that I'd like to sort first)
7. Fuses checked several times and all are ok.
8. Both rear windows are getting 12 volts to the switches and the switches work when plugged into other recepticle thingies.

I'm stumped at this point.

Ideas? Insights? Thank you.

Same symptoms for me. I had broken wires in the door hinge. They are hidden inside woven insulation in the accoridan rubber thing between the car and door. I added new wire from the pillar to the door.

I've got 12 volts to both window switches, so the wires seem to be fine. See also #5 above ;-) I like the idea of just adding a new wire! I cut the mesh stuff off and checked the wires after pulling them all the way through. No breaks I could see.

Your windows will work without the key so do mine ,normal with w124 .You do have a relay for windows .Regulators are a problem after a few years,and they do fail .Easy to fix .More of a problem is removimg the door car and refitting them back in place after.The metal gear wears out, but can be welded up to standard. Or just replace the whole thing .Just had a thought ,i have only replaced the fromt ones on my 124 .The backs are not installed on a metal frame with the motor , but on frame with cable type draw string and pullys ..

I'm thinking it's the regulators. Wish I had a way to get 12v power to them via a jump-box or something to see if they are indeed the culprit. Ideas? The whole shebang probably needs lubrication as well.

4. Console switches test ok and I can hear the convenience relay clicking when I engage the switches for the rear windows

Have you checked your convenience control module?

The only way to supply power to the motor directly is to remove the door panel which is not all that hard to do.

Yes sorry I did check the CCM. Looks perfect at least to the naked eye. No discoloration/burning marks where it could be dirty/failing. Anything else in particular that I'm looking for? I read a thread on some forum (dunno which one) that discussed what to look for.

Door panel removed on near/driver side without problem.

Could you recommend a way to get 12v. directly to the motor? Shall I just use the power already going there with jump wires? I guess I'm answering my own question here ;-)

I seem to remember a terminal block with a two wire connector which is exposed when the door panel is removed. There should be no voltage there unless a window switch is depressed. Applying voltage and ground one way opens reversing the connections closes. That would be the first thing to check. Long wires from the battery would work.

If you are going to apply 12 volts to the window motor at the terminal block, make sure you disconnect the wires. If not, there will be a direct short. The relay in the convenience module shorts out the window motor when disengaged to act as a brake. Same thing applies to pre convenience module cars except the shorting is through the switches.

Yup did that. Direct power to the motor gave me no love, but I could hear the CCM clicking (same noise as when you engage window switch). I've pulled out the regulator/motor and taken apart the motor. Old cruddy grease, but the motor brushes look ok. The area where they 'touch' is pretty dark with carbon dust so I'll clean that and put it back together and see if I get anything.

If you disconnect the motor wires at the terminal block and hook 12 volts to them the CCM should no longer be connected so it should not click.

The caveat here is that the 12v power I used was the two leads that feed the switch itself, and I'm assuming they come out/through the CCM itself...so...:undecided.

I've taken the motor apart now and am cleaning everything up and will put it back together and see if that helps. Fingers crossed.

Also have new fuses on order to just go ahead and replace all of them and clean up the contacts in the fuse box. Just last night the wipers stopped and it was fuse #2. A jiggle and a wiggle and they worked again. That has since been replaced.

Ok, all cleaned and put back together. I got the same results as before. Hook it up to 12v and hear the convenience control module/relay 'click' but nothing else.

And the 'convenience' feature is now intermittent. Or perhaps I have only started noticing it but it's been this way for some time. Sometimes the window switches work (for front windows and rear left) when the driver's door is closed...but sometimes *only* when the driver's door is open.

Shall I just assume it's the stupid relay and buy one?