Questions about comfort/convenience system W124
 

Hi all!

I've got a new-to-me 1992 300D that I'm trying to iron out the wrinkles in. I have a cluster of issues that I think are related, they include:

• -window can't be rolled down only part of the way; once you hit the button it's like an "auto-down" feature has been activated. If I put the window switch into the "up" position while the window is rolling down, this will pause the auto-down, but as soon as I release the up switch, the window resumes going done. Once it's all the way down, you have to cycle ignition switch off and back on in order to roll the window back up
• -there is a completely random clunking sound (it sounds like the antenna motor activating, but it's not) that sounds like it's coming from the area of the left rear trunk, although it could also be under the seat or in the left rear door. It's so infrequent I've been unable to find it.
• -Battery is nearly new and correctly sized, but an as-of-yet found battery drain will kill the battery if car sits for ~3days or more.
• -I was driving around the other day and the sunroof, without any input from me, opened halfway. I was unable to use the switch to close it until cycling the key switch off and back on.

I don't care about the central locking system working, any "convenience" features, or any sunroof functionality. I just want the windows to operate with the switch, and to hopefully eliminate battery drains.

The questions:
-how is the convenience system controlled? Can I remove controlling elements like relay etc to disable the gremlins? Where the heck are these components located and what do they look like?

Thanks ahead of time for the help folks!
Brad

Can you see the red charging light in the dash when you switch on the ignition ? And dose it go out as the car starts up ? Also pull the regulator from the alternator 2 screws and check the carbon brushes have not worn away ..Take earth leead off the batttery before to play with the alternator ..

Convenience relay is located under the rear bench seat on drivers side. Sounds like you could have a faulty window switch. Your model year does have the one touch auto down feature, but from your description, it is acting strange. If I remember correctly, you can’t just remove the module/relay from under the seat or you will lose power to the windows. I suggest pulling the module, inspect it for moisture, make sure it is getting a good connection, plug it back in and see what happens. If still not working, these modules are easy to find at most pull yards and were plentiful on fleabay and reasonably priced. I believe any convenience relay from a 1992-95 will work as well as 94-97 W202, but not positive. Actually, the cab module is different, but you won’t find one of those floating around, if you do people are asking crazy money for them.