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Electronic problems

It’s an '86 mercedes 500SL (euro model). I recently had the battery removed for a check. I had starting troubles and thought it might be the battery. It checked out OK, but ever since it was replaced the power windows only work when a door is open! The instrument panel gauges don’t work, including speedometer and odometer, but the clock works fine. The turn signals don’t work and the brake lights don’t work. What would cause all these things to go out at the same time???

Accidently installing the battery backwards for a brief time.

Sounds like a ground problem to me.

Start from the battery negative terminal and inspect the ground wiring, any wire strap(s) from the car body to the engine, any ground wires that come out of harnesses and bolt to the body or engine.

If you haven’t checked the fuses and fusible links yet to see if there is a problem there then I suggest you do that. If there isn’t a problem there then there may be problem with the grounding as Circuitsmith suggested. You could try adding a ground jumper wire from the battery and to a good ground point to the dash area and see if that helps.

The window problem may be due to a broken wire in the door jamb. That is a very common problem with the power windows after some time. If that is correct you may be able to replace the small harness in the door.

Thanks for the help everyone. Turns out there was a short in the wiring at the trunk hinge. This kept blowing fuses. Once I fixed the short and replaced the fuses, all is well.

Glad to hear you got it fixed and thanks for the feedback.

It’s nice that you found where the problem was; but, HOW did you find it? The trunk lid is a fair distance from the instrument panel. What’s the connection?

Just lucky. Brake lights and turn signals didn’t work. I was noodling around in the trunk and noticed the short…taped it up…new fuse…bingo!