Please help with windows! - PeachParts Mercedes-Benz Forum

dieselbryan · #1 10-22-2007, 10:47 PM

I have an '85 300d turbo the back windows do not work (for about 6 months now). The shop good not find a break in the wiring and all switches are new, If the motors are defective would I be blowing a fuse when I hit the switch? The 2 widnows broke down about 3-4 weeks from each other. Thanks Bryan

jkoebel · #2 10-22-2007, 10:58 PM

Are you blowing a fuse when you hit the switch? Or was that a hypothetical?

dieselbryan · #3 10-22-2007, 11:01 PM

Yes, when I hit the console and door switchs the fuse blows. thanks Bryan

dieseldiehard · #4 10-23-2007, 01:10 AM

Its possible the wires where they pass thru the door jamb have insulation that has cracked and two or more wires are touching and shorted. This is quite common. 124's are worse because the wire was bad from the factory

The LF and RR doors are on one fuse. Likewise the RF and LR doors work on one fuse so that is helpful sometimes in troubleshooting a blown fuse.

The best way to diagnose this problem is remove the door panel and disconnect the motor. then replace the fuse and press the switch on the console. If the fuse blows again its probably bad wiring. Sometimes you have to wiggle the rubber boot that carries the wiring to make it short out.

Its possible the motor is shorted. You can run the motor off a small gel cell, thats what we do to run the windows up and down on doors that are off a car. Or you could run a zip cord to the battery, using a 15 A fuse for safety. There is a two terminal place the motor is connected to and the battery goes to there momentarily.

I just fixed a LR door that someone had tried to repair this type of problem and they used small wire that melted, it was a sad repair

To do the repair properly You have to cut short lengths of 16 gA wire (any color is fine) and solder the ends of the existing wires after you cut the bundle and cut out about 2 inches of the fatigued wires. Do each wire individually using shrink tubing (avoid using electrical tape here) to insulate the joints (overlap the wires, don't try to get fancy and make knots or something.
You can now use tape to wrap the whole mess and a few more tie-wraps.
Then stuff the excess wires back into the doorjamb. The rubber bellows can be salvaged if its not already torn (most of them are by now) but it makes the job a little harder. I went into shock the last time I asked the dealer what
one of those rubber bellows costs, besides you have to pull the vac lines if you replace one, what a PITA that would be so forget that.

JimFreeh · #5 10-23-2007, 06:52 AM

If your front windows are working, then the problem is isolated to the rear window circuit.

If I understand you correctly, you blow the fuse whenever you hit the rear window switch.

That sounds a lot like a dead short. If the motor was bad, you should hear a clunk or bump as the armature tries to spin.

As mentioned, it's easy to test the motor itself. Pull the door panels and look at the lower front corner of the inside metal skin. You will see an insulated connector with two wires attached to the sheetmetal. Pull the connections and apply 12v power to the two wires that go to the motor. switching polarity will determine which way the motor turns (up or down).

Also, perform an ohm check of the wires leading back to the b-pillar to check for a shorted wire.

Jim