Thanks again for the help on the OVP related issue. Two new ones.
1. Neither front window budges. Both back windows work from the control on the console. Swapped switches:No joy. Since the back windows work, it is not a fuse issue (I assume) because they fusing is on diagonal windows. Both windows worked last fall and I did not use them during the winter.
2. Last fall I moved the passenger side front seat back angle way forward in order to carry some odd shaped articles. Now it will not move toward the recline position. Anyone riding in that seat would have to bend forward.

Any ideas would be appreciated.

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87 300D 265Kmi
Factory rebuilt crate 603.96x engine at 200K

In both cases cleaning the switch contacts would be a prudent first step, Radio Shack used to sell a small aerosol can of contact cleaner. Pop the knobs of and the plastic covering and you can direct the straw into the small opening nearest the switch operators on the seat control.

Window controls seem to indicate the electrical is not getting from the switch to the motor, could be the window lifts are simply frozen in place due to lack of operation or could be no power getting to them. I'd pop the door cards off and using a test light determine if power is getting to the motors. If not it could be a wiring issue. If power is getting to the dual "green & black" wiring connector in the door shell it would point to the lifts being faulty.

Common problem is wiring from the switch to the window lift wears/breaks at the point it passes through the rubber accordion conduit between the chassis and the door.

You might just try the window controls forty or fifty times. May just be rusty. I had a similar problem on my '81 300SD with the driver's seat. So much so that I removed the seat, turned it upside down, and hooked the motor up to my battery charger. For some reason it just started working again - I actually did nothing to it. Put it back in the car and it has worked for another six years or so.

So it might just be due to inactivity.

I'm remembering windows are cross wired or IF is powered by the same fuse/relay as the RR. You could have an issue with switch, motor or door wiring.

The wiring may be in the FSM. Run the etm.swf file for your car and the off will download to your browser's download directory.

Pull the door card and it is obvious how the motor is wired.

As I remember they are wired front driver to back passenger - and front passenger to back driver side. So if your front driver window will not open but the back passenger does, then it is not a fuse.

I thought I'd have to do the entire cleaning of the contacts as others mentioned. Much to my surprise, when I went through all the work to get to that area and had the plastic cover panel off, it worked fine. The problem was that the plastic cover piece was preventing the switch for the back recline from moving back far enough. So I drilled into the plastic a bit to make the hole bigger.

Mind you that I had to do this a few times. So if you only want to do it once, drill enough out, but not enough that the buttons won't cover the hole. Just make the hole bigger going backwards and also up a little so the control can move enough.

jeff
1991 300d

Before ruling out fuses, try installing gold-plated ones. The silver fuses the factory installed in my 300D's have caused many problems w/ windows and sunroof not operating. I could fix that by sanding the fuse tips, but eventually gave up on the silver's. In your case, perhaps the front window motors require more current than the rears, though strange both circuits would fail at the same time.

Next time you unplug the switch, use a multimeter on the switch pins. If a "voltage loss" issue, you will need to monitor w/ the switch connected, which you can do by pulling the connector back enough to get at the pins. That is how I found my 12 V supply from the fuse panel was getting drawn down the first time I had issues. If you pull the door panel, you will find a terminal for the motor wires (if like my 1985). Verify continuity of the wire from the switch. In one car, a wire had broken where they bend at the door pivot.

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1984 & 1985 CA 300D's
1964 & 65 Mopar's - Valiant, Dart, Newport
1996 & 2002 Chrysler minivans

but I do not know where to get them. Any suggestions?

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87 300D 265Kmi
Factory rebuilt crate 603.96x engine at 200K

For the window issue; if you determine that it is in fact the regulator that is the faulty part; take a look at the link below for the procedure on replacing it. Please let us know if you have any questions! Lastly, if you're looking for a specific part; like the fuses - feel free to give us a call at 888-280-7799 and one of our MB part specialists will be happy to help you out with them or can suggest an alternative if the part is NLA. Best of luck!

Mercedes-Benz W124 Front Window Regulator Replacement | 1986-1995 E-Class | Pelican Parts DIY Maintenance Article

It's not the fuses if both back windows work. The windows are cross wired: one fuse controls left front and right rear, the other controls right front and left rear. Never understood why, but maybe it was done just so I could say "definitely not the fuses".

What you're going to have to do is remove the door card. There will be a two wire juction somewhere on the door panel. BOTH contacts should be 12v+ without touching the switch. BOTH of them. If one or both of them are cold, then that's one problem.

Have someone hold the switch in the up position. One of the door contacts should remain at 12v. The other should go to GROUND. That's right, GROUND. If your assistant flips the switch to the down position, the polarity will reverse: the ground will be on the other terminal. If this is happening as I've described, then your problem is the regualtor motor. If this isn't happening, it's the switch.

You can also disconnect the window motor at the connector then run a test wire from the battery to note whether the motor turns. The motor has 1 of several drive gears that actually is what moves the regulator. The teeth in the regulator gets stripped or the motor craps out.

The regulator is specific to the door. Any regulator from a 126 81-9x will work as long as motor and regulator are kept together. You can look up the various gear teeth on this sie if you're interested. Cheaper to just get a regulator out of a yard.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.