About the electrical difficulties you are experiencing...

Bear in mind that for the most part, each of those components you have mentioned - windows, wiper, and so on, are energized by several different cicuits. As an example, Fuse "G" protects the front window circuit while fuse "H" would protect the rear window circuit; fuse number "2" protects the wiper system, and so on.

On the 1990 through 1992, a convenience control module is located under the rear seat on the left side. Granted, your 124 is an '87. So, for '87, two relays ((not fuses) (position "F" and position "H" )) are found in the "component compartment." This is what appears to be a box measuring roughly 4" X 6" and is directly aft of the fuse box under the hood on the left of the car. Convenience relay "H" is in the circuit that powers-up turn signals/hazards, the heated rear window, and the wiper motor. Convenience relay "F" is the relay for both front as well as rear windows. Looking at the relays (once the lid has been removed by backing out the six retaining screws), you will see three columns. "F" is in the center column, toward the firewall and "H" is in the center column toward the nose of the car.

That said, and really more to help you determine where these items are for troubleshooting purposes, I believe also, that interior lighting is handled via Convenience relay "H" and here's my guess: If the car is new to you and its history is unknown to you, I would certainly begin with a test of the fuses as well as the relays mentioned (checking all would be wise, too). With the driver's door open, remove the jamb switch. If I recall, the factory installed alarm system was an available option. I would want to know if someone previous to you had removed the jamb switch in order to power-up an aftermarket accessory of some sort - including an aftermarket alarm that has not only gone south but seems possible that it's taking other vehicle systems (lighting, wipers, windows...) with it.

What I am getting at is that you've either got a faulty jamb switch, faulty relay(s), and/or non-standard, non-workmanlike wiring; non-acceptable.

If your car does, in fact have a factory alarm system, you'll know this by seeing two jamb switches in the driver's door jamb; one directly above the other. Unfortunately, I don't know which one is which. I am sure "gsxr" or some of the '87 300D folks who've been around far longer than I will have that answer. If you spot only one switch, I would begin to suspect bogus wiring behind it - especially if the fuses and relays check-out.

The jamb switch is easy to remove and can be carefully pulled away from the jamb with a couple inches of its wiring in order to inspect. Use a good meter to check for Ohms in both the open and closed sides of the switch if at first you don't see what looks like obvious, extra wiring that didn't come from the factory. Temporarily remove the wires from the switch to check for Ohms.

One other area to look is above the driver's legs, behind the black plastic covering panel. Carefully remove that panel and visually inspect every square inch of that area in all its nooks and crannies. You are looking for again, obvious extra wiring that may appear to have been installed at some point after 1987. If you see something, try to make a note of where the wire(s) originate and where they terminate - then make another post here to let everyone know what you've found.

Apologize for then lengthy post but hopefully there's some help in it somewhere.

Oh, and congratulations on finding a really great Mercedes and welcome to MercedesShop!

Tom