Hello all. I have been working to get my power windows functioning again a few minutes here and there over the last month. Here is what happened along the way. I will update with more pictures over the next few days.


I purchased a 1986 300SDL in early June and had a few items to work out. This has been a little more involved than I had anticipated. The power windows were working perfectly when I started working on the first project.

First order was to get the climate fan to work w/o blowing the fuse. research lead me to installing an external 30 amp fuse. Opening the fuse box to expose the wiring, I found a melted, hacked mess. Unbolting the wires to #16, I decided to bolt them to an auto resetting 30amp breaker. All said and done, it worked.

While in "the mess", I tried to fix a few other wires.





and the fusebox from above.



W = Window relay.
red circle = #16 fuse Climate fan and #c,d power windows.
Green Arrows = phillips screws to open fuse box.

Other than the fuses being unreliable, I love the way this fuse box is modular. Each section detaches from the next. Relay plugs detach from the main body.
This is great for repair and/or upgrades and swaps.

I clearly need a new fuse box assembly. For now I am focused on making this a usable car and may tackle the fusebox project during the winter.

For now, allow me to continue.

The other day a friend was over for one of my 20-30 minute "try to fix the power windows" sessions. He suggested we start all over. This proved wise.

Note in this picture the coloured sections.

Quick over view.
Note upper right corner, Fuse 17 is energized when the key is in Run or on.
If there is power to one side of the fuse and the fuse is good,
power goes to the black/yellow wire that turns on the Window Relay.
With the Relay on, power is sent to Fuses 'c' and 'd' through the Red/Yellow wire.
From there, power moves on to the center console switches.

So we went back to the drawing board and started at fuse 17.

No power. (We may be on to something.... )

Opened up the fuse box and found there wasnt a feed wire to fuse 17 at all. I must have removed it accidentally while dealing with the earlier "mess".
As a test, I bolted the wire that goes from the fused side of #17 (and switches on the relay) to the protected side of the circuit breaker mentioned above.

Ta Da ! power windows. We heard the relay click and we new we were in business.

Carefully studying the wiring diagram gave me a good understanding of how the system worked. I dont know where all the wire are located, but I know how it works. Next will be to find the missing feed wire and then figure out why the moon roof also doesnt work. I am guessing same error on my part early on.

I am still looking for a set of leather seats for my 86 300SDL if anyone has a clean set. Email/PM me.

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Wanted: 98-99 OM606 car or motor only.

83 300TD (need rear wiper assembly dead or alive)
98 E300D
87 300TD (looking for set of wood trimmed W124 door panels in black)
86 300SDL Need W126 Blue leather seats and door panels.

Generic answers:
Pull the Window Fuses and check the Tips of the Fuse and where the Fuse contacts. (See Pic of what stopped 2 of my Windows from working.) Get rid of any Fuses with a Plastic Body.
Make sure you are getting power to the Fuses.

Pull the Window switches and clean the Contacts (scraped mine with a small pocket knife) inside of the Switches; there is a few DIYs on that.

Pull off the Door Panel and inspect the Window Regulators (on my 123 the Window Regulator Mounting Plates were bent and warped causing the teeth to wear badly); if they are in bad shape your Windows will stop.

Thest the Window Motors themselves by connecting the 2 Window Motor Wires to your Battery to see if you can operate the Windows. Reversing the wires on your Battery reverses the way the Motor Turns. (Unlike your Starter Motor your the Ground is not part of the electrical circuit on the Window Motors.)

If the Switches are good and the Motors are working broken wires where the hinge in doors could be the problem.

I have yet to read of anyone having to replacing the Window Relay so unless you have an other one already to swap and see if that restores power I would look there last.

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84 300D, 82 Volvo 244Gl Diesel

Diesel 911, Thanks for the tip. My starting this thread was to provide a DIY covering what I learned. As I mention above and many others in this forum, the fuses are often culprit. They may look good, but they could be oxidized. It really is best to buy a large box that includes all amperage's and replace everything, keeping spares in the glove box.

I have also gone through, cleaned and rebuilt many of the switches on my W123, 124, and this 126. Again, helpful advice.

Another point of failure is the plastic slider in the regulator assembly. My left rear window comes loose from the regulator and drops into the door if lowered too far. An inexpensive replacement can be installed if you are crafty enough to figure out how to "peen" over the new pin. I still have to perform this task. I have a DIY coming for that.

__________________
Wanted: 98-99 OM606 car or motor only.

83 300TD (need rear wiper assembly dead or alive)
98 E300D
87 300TD (looking for set of wood trimmed W124 door panels in black)
86 300SDL Need W126 Blue leather seats and door panels.