I recently replaced my 1980 300SD with a 79' and I'm in the process of working out its kinks. I do still have the 80' and am using it as a parts car.

Just a short backround story for reference. The previous owner had the car as a project, and kept it garaged for a year or so. He was in the process of replacing all the door seals, as they all leak. Though when I bought it, the only door "finished" was the front passenger, though it still leaks.

Anyway my current issue is this. The driver side window does not opperate. When I first picked the car up, it did work, but very poorly(slowly). After the car spent its first couple nights outside in a year, the window stopped working alltogether. I assumed this might be due to water in the door, possibly causing a short. What stumped me was that several times on the cold start of the day, the window would work for a few seconds then, nothing. It seemed to do that for a couple weeks, but I have been unable to reapeat this since.

I now have the door panel off, and I sanded the points on the wires leading to the window motor, but still nothing. All the other window motors seem to operate.

I have a service manual on disc for my car, but I seem to be missing the wiring diagram for the power windows. The reference table in my service manual says its diagram 8, though mine goes right from 6 to 9. I also seem to be missing the main fuse box diagram thats normally on the underside of the fuse box cover. This would be very helpful aswell.

Any troubleshooting methods, suggestions or links to my missing diagrams would be greatly appreciated. Thanks very much!

The window regulator might be gummed up or not operating smoothly. My 240D has an issue with the driver door window not wanting to come down. For awhile I though it had to be electrical, because sometimes it would work, and other times not. Come to find out, the problem is the actual track that the window slides up and down in was sticking the window shut and not letting it go down. I very lightly greased it, so as not to smear up the glass. It now works every time. This is just my experience, your problem might be different all together, but its a few ideas I guess.

First, always check the fuse.

The problem could be, in order of ease of fixing and probably likelihood, a switch or electrical problem, a lubrication problem, or a motor problem.

Push the switch up, then down. If the window is all the way up, you will notice that the lights do not dim when you push the up position, but will when you push the down position. Thsi means that electricity is getting to the switch, but the switch is not passing enough current to the motor for it to function. If the window is all the way down, the reverse will be true.

If it is the switch, remove the switch, look up the directions on how to clean it on this site, and add a small dollop of dielectric grease. Connect the leads from your problem window to a working switch to test the switch.

When you remove the wooden console, be sure to unscrew the button hidden in the middle of the rear part of the console, or it will break.

It is possible that the wiring has become abraided and it is not passing enough current. You can test this by taking off the doorpanel and comparing the resistance at the lead going to the motor with the reading at the switch.

It should be easy to see how much grease is on the tracks. My guess is that most of the grease on a 30 year old car will have become decidedly unslippery.

The motor is your last possibility, barring some plastic grommet things that sometimes become damaged, and pieces of which should be found at the bottom of the door. When removing the door panel, do NOT force anything. Be especially careful of the door pockets. The plastic things that hold then on are prone to break and even more prone to be be very difficult to repair.
I'd do a search on "remove door panels"


A junkyard will be the cheapest place to look, a dealer the most expensive. A search online will reveal prices between $170 and $400 or more. You will have to unsolder and resolder the connections, or at least I did. You can try resurrecting the motor with proper lubrication. Start with a lightweight oil, then use some dilithium grease, unless you find a better recommendation on this excellent forum.

Best of luck!

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Semibodacious Transmogrifications a Specialty

1990 300D 2.5 Turbo sedan 171K (Rudolf)
1985 300D Turbo TD Wagon 219K (Remuda)

"Time flies like and arrow, yet fruit flies like a banana"
---Marx (Groucho)

My 83 300sd came with one operable window. Pulled the motors, opened them up, cleaned out all the rust and dirt, greased 'em up and had 4 working windows about 1 1/2 hours later. Greasing the run channel is also a great idea. The regulators are also notorious for breaking in these cars also, too strong a motor for the aluminum.
So, when you have the door panel off, remove the motor, put 12v to it and see if it spins. If it doesn't, remove the end cap on the motor and see what kind of crap you've got in it. Get the stuff out, grease it up and put voltage to it again and see if you get lucky.

Awesome! Thanks so much for all the quick and thorough responses. Many good ideas I'll put to the test right now, and post my findings. Thanks again!

Just a quick update. Pressing the switch does not result in any lights dimming, nor is there any noise from the window motor. I have not yet found a diagram for the main fuse box, so without testing each, I don't know what they belong to. I will remove to motor tomorrow, and see if the leads on the passenger door run it.

I tried cleaning out the motor but it still doesn't want to operate, so I'll be swapping it with the one in my 80' 300SD. Next task is working on my struggling sunroof motor.

There are three things to check
1) Clean the switch - not hard but be careful not to loose parts
2) Check the wires where they go from the door frame to the door -they break in this area
3) The bushings in the motor dry up and get stiff

These pictures might help. The last picture shows the connector block in the door, this is a good place to run a jumper to to test the motor.

Attached Thumbnails

     

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1983 300SD
200000miles

I have to replace three window motors but they are hard to find and quit expensive. Used ones in Germany is USdollar 100. Whats the price in US? Anyone selling perhaps? Please contact me.

But I will try to take them out and inspect how it looks inside. I did so with the windscreen washer, and got it working. Thanks.

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T-Bird Rules if itīs a bike...Mercedes headlight...makes it legal here...

I fixed the power windows in my 1979 300SD by removing them! Now I have manual windows with cranks that are much more dependable and less headache to work on.