C124 window issue

[Dec]

There is a Convenience Control unit under the back seat, it contains 8 relays, one to raise each of the windows and one to lower each window.

When you push the driver’s window switch for DOWN, the switch energises the driver’s down window relay, the relay points close and deliver power to the motor to lower the window.
When you push the driver’s window switch for UP, the switch energises the driver’s up window relay, the relay points close and deliver power to the motor to raise the window.
Having 2 relays for each window reverses the polarity so as to enable the window motor to reverse direction so as to raise or lower the window.

One possibility why your window is not coming down… if its in the fully up position… is that the relay that is responsible of bringing it down has a dirty or burned points and so preventing the motor receiving any power.

You could open the cover of the Convenience Control as pictured below, don’t unplug any of the plugs, the unit will be live even if the ignition is off so don’t let it touch any metal. With the ignition on, close each relay points with your finger to ascertain which relay belongs to which window or operate the window switches, each relay will click when its switch is pressed, this will identify which relays belongs to which window.

When you identify which relay belongs to the driver’s window you will need to check that that the relay points are clean and undamaged, it will be the down relay for the drivers window that may be faulty… that is, if the drivers window is in the fully up position when you are testing it.

The above is a plausible explanation as to what’s at fault, however it could be something else that’s the problem, like the vacuum pump or the window motor.

Dec

 

[LCHutton]

Dec-
Thank you for your reply. I will check the relay and post back.
BTW, I'm in the US so RF is the passenger window. I do not know if it had auto-down but if it was supposed to have it, it did not work.

After removing the door panel I found the slide had come out of the guide that is not directly attached to the window. That could be the cause of the window not going fully down. Then after a few attempts, it would not go up. Now, I can check to see if the problem is the relay and not the motor.

 

[Dec]

I didn’t read your two posts in the link in post #20 until now, it all seems to be more of a mechanical fault with the mechanism (stuck) rather than an electrical fault, check the relays anyway, that will be easy, except for wangling the relays out of there shell.

Dec

 

[LCHutton]

Dec,

I checked the relays 5 & 6 for the passenger window and each responded to the appropriate switch position. The relays are sandwiched between two boards that can be separated to see the relays. Everything looked brand new in this 22-year-old car.

Are there torque switches or circuit overload sensors to prevent overtravel and/or to stop if something is blocking the window?

 

[Dec]

Dec-
Thank you for your reply. I will check the relay and post back.
BTW, I'm in the US so RF is the passenger window. I do not know if it had auto-down but if it was supposed to have it, it did not work.

After removing the door panel I found the slide had come out of the guide that is not directly attached to the window. That could be the cause of the window not going fully down. Then after a few attempts, it would not go up. Now, I can check to see if the problem is the relay and not the motor.

From what you say above, it does sound like the mechanism is stuck somehow and the motor is then meeting resistance and shutting off.

Not sure exactly how it works but the motor has to sense resistance when the glass gets to the top of the door otherwise it would just burn itself out if you were to kept your finger on the switch after the glass reaches the top.

Were you able to see for sure that the DOWN relay points were clean and undamaged?

Dec

 

[optimusprime]

window

I replaced mine .I held the window in the up position with wooden scotch and tape over the top of the door .Take pictures , and mark up the bolts and the place they come from with felt tip pen. Do it step by step as you go through the removal . Just be sure it is the motor before you remove it all .I removed it all the regulator the lot out of the door ,and fixed the other one right back in . You will have to use the power to locate bolt holes because they wont line up after you fix the new part back in ,keep you hands away from moveing parts when you do. Most important is seal the door face after the job, with the membrain you removed to start with ,if you dont rain water will find its way in to the foot well. Also while you have this all off greas up your door straps [check stays] easy while the cover is off the door. I removed mine and cleaned it up and and put on oil and grease ,then pop it back in.By the way, mine did work after i put 12 volts to it in the garage ,so make sure it as a good contact to it before you pull it out the door. .

 

[LCHutton]

Update:

Dec & optimusprime,

I have the window up and can hear a slight air leak at speed so it's not fully closed but there are no visual gaps. I could live with it as-is.

However, I have decided that before mounting the door panel I'll clean the relay contacts and then re-check the motor. In my original test, with the key in the on position, I had around 12.5 volts at each of the wire terminals. This value drops to zero on one terminal when the up or down button is pressed. I think that means the motor uses the door frame instead of a ground wire for ground and I think the motor was not grounded when I tested it. Therefore, I will remove the motor and regulator again to retest the motor. If it works, I can re-mount it with the window down as described in the "How To" section.

In addition, I did not re-install the thick white plastic washer between the motor and regulator. Anyone know where it goes?

 

[Dec]

Both wires, that go into the motor, go back to the convince control unit where one will be earthed when the polarity is switched for up to down.
The motor is probably ok and this fault is with either the window switch or in the convince control unit.
If the driver’s window switch is identical… it may not be… to the passenger window switch then you could swap them round to see if the passenger window becomes faulty.
That 12.5v you mention is normal, its the polarity being switched when the switch is being moved from its neutral position to up or down.

If you can’t find and fix the fault, you could rewire that particular window motor which would then become independent to the rest of all the other windows, see the video below.
Play this in full screen… https://www.youtube.com/watch?v=EYuhk7urqFE

Can’t help with the plastic washer, if you could put up a picture of the washer in relation to the window motor assembly, someone may be able to help.

Dec

 

[daibill]

As an update to the update, although I had voltage to the passenger window, the way I fixed the passenger motor was to hit the motor area with a hammer. Worked from that point onwards...

 

[LCHutton]

Drive Gear missing teeth

I found it is extremely difficult to install the regulator with the window in the full up position so I thought if I tried it in the down position the motor stress would be reduced allowing it operate. It moved a little bit and then stopped mid-position.

I then took the motor/gear box apart and found the white nylon internal drive gear was missing a few teeth. That meant it could go almost one revolution before the motor's worm gear hits the empty spot. There are 10 teeth on the pinion and about 42 on the regulator so it would take 4 full revolutions to close the window from the down position and/or I'd have to mount the regulator with the window more than 3/4 up and hope it closes fully before the worm hits the spot missing teeth.

Not feeling lucky, I bought a replacement motor on eBay for $35 USD.

 

[Dec]

Well done for taking it apart, would not have suspected that as the cause of the problem.

Dec

 

[LCHutton]

New motor installed and operating well. Now I need to put the door panel and have 3, white clips that I don't remember where they were located. Any ideas?

Since I didn't expect this project to take this long and since there is a "HOW TO" on this website, I did not write down where each part was located. My mistake.