I know it's blasphemy and all :) but my girlfriend's cousin has a Mercedes 190e and it has some wiring issues.
I've looked around on google but haven't found any support boards (besides wikipedia) and don't know really anything about mercedes systems.

A couple of the issues:

*Blinkers don't work:
-A combined relay controls the wipers, flashers, and hazards, and has 3 separate relays on it and some circuitry that looks like it includes a computerized timer. Because of the timer, I'm not sure if there's any way to provide voltage to the relay and see if the relay works. I noticed a lot of them for sale, so it could be a point of failure. It has a fuse box with the pinch fuses like I've heard about on the 240's, but that's not an issue - the circuit works for the other accessories on it. The other suspect is the switch, but I wasn't ready to attack the steering column last weekend, and the way to get it apart is not apparent. The dash lights are functional (removed and tested) and the bulbs and wiring from the wire box is good.

*Possible idle/ecu problems.
I noticed the wiring's outer layer (there are 2) of insulation is brittle. The engine fan clutch works fine, but doesn't get voltage. The ECU tests the idle control valve (sounds like my 740's) after being on, but not running for a few seconds. While running, the idle oscillates.

*Automatic Climate Control... looks like they all suck.
He's got auto climate control and numerous vacuum leaks. I could hear one behind the dash when it was running and the pcv tube is split at both ends and brittle.

Other stuff too, like stuck windows and sunroof.

I'd say move on to another car, but he needs it and needs a job.
And as of Tuesday, it's not running.

If anyone has a recommendation for a forum or a FAQ or whether haynes or chilton manuals are useful, please share.

Cheers,
Will

--
1990 740 Turbo, on its way to stock specs, maybe beyond