90 W124 - ALL windows stop working intermittantly - PeachParts Mercedes-Benz Forum

Andy_M · #1 05-02-2011, 03:05 PM

Could use some help with this one. in my 90 300E all 4 windows stop working intermittantly. Sometimes they are fine, sometimes you put them down and when you try to put them back up they are all dead. Leave the car for a few hours and sometimes they will work again...sometimes not until the next day.

I have checked fuses and ground points....they seem fine. Have checked the switches....all seem fine. All windows work when they work, so window motors don't seem to be the issue. Can not find any evidense of a short anywhere. This problem started almost a year ago and got more and more frequent over time. Now it is almost a daily issue. I can't find the culprit.

One thing...when they are dead....clicking the switches (any of them) produces a "click" sound from under the rear seat. I believe this is the location of the convenience control unit.....I will check this out next.

Anyone have this happen to them before ?

TheDon · #2 05-02-2011, 03:06 PM

Might be the convenience control unit going out. I haven't had this issue but if the fuses are fine, the switches, etc then you might want to check that control unit.

babymog · #3 05-02-2011, 11:08 PM

I believe I have a working spare, if yours is bad let me know.

Check for water under the rear seat, more of a 126 problem but you never know.

Andy_M · #4 05-18-2011, 06:57 AM

Well, I've exhausted every source of the problem that I can think of, other than the control unit acting up intermittently, and nothing has corrected the problem. Going to pull the rear seat and get the numbers off the unit. Other than that,and an obvious visual check of connections, etc.(which I am sure at this point won't show me a thing) what else can I test on the control unit to diagnose it ?

mbdoc · #5 05-18-2011, 08:14 AM

Best diagnosis at this time is by substituting a known good control unit.

silversleeves · #6 05-18-2011, 10:59 AM

Have you checked the state of the wires running through the doors? The wires running through my B pillar were cracked and brittle producing intermittent functioning of my rear windows.

Andy_M · #7 05-19-2011, 01:11 PM

I get intermittent failure of the entire circuit. NOTHING on the window circuit works, or everything on the circuit works fine. Nothing in between

compu_85 · #8 05-19-2011, 02:05 PM

My suggestion: Remove the CCU, open it up, and look for cracked solder joints. If you see cracks it could be an easy fix

Of course get all the windows up before you take it out

-J

benzworldrefuge · #9 05-20-2011, 09:38 AM

How about the ignition switch. I know it sounds unlikely but my climate control either works or doesn't depending on jiggling the key in the "run" position. I'm replacing the switch this weekend but thought maybe there is an outside chance this problem has a similar cause to what I am seeing (88 300E)

Andy_M · #10 05-20-2011, 10:14 AM

Thanks guys.

compu_85....I will do that. Nothing to lose. Have to replace it anyway, so why not.....

benzworldrefuge....a while back I would have agreed that might be the issue, but we have tried everything...wiggling the key, the switches, pounding on the doors and console, using the key from outside, I even ran a "backup" ground out to the engine compartment from the center console to MAKE SURE the ground under the console was good.....nada. Does it whenever IT wants to....usually when it is raining out....(but of course, not always.)

babymog...When you have a chance, PM or email me (atmorris@ptd.net) on that spare you have....how much you need for it and any other info I need to make sure its a match. Thanks.