Axe Murder

Hello. The rear wiper on my -09 E280 wagon quit working.

I was adviced to a) check the fuse, then b) see if the motor operated with 12VDC applied "manually". If those fails, c) look for broken cables.

Two problems with that: where is the fuse? There are like four fuse/relay boxes in my car, and all the diagrams I see list only a relay (#4 in the trunk compartment) for the rear wiper. No fuse?

Second problem: I removed the inside fairing, and the wiper motor has three cables. Which ones do I connect plus and minus to? I don't want to fry something.

I have scoured the web for some information about wiper motors, because they seem to be quite generic, but most just show how to screw it apart, or explain to me like I am an idiot that they can indeed break and I am welcome to purchase a new one on their site. And then we have this:

"IIRC, the motor has power to it when ever the key is on and is controlled by a digital LinBus controller that is built into to the motor. If you put 12 Volts to the motor, you would burn out the controller if you put the voltage to the wrong contacts." (although that was a VW).

So I don't know what to think.

Thanks in advance for any wisdoms shared.

Axe Murder

The connector to the wiper motor has three leads: orange, red and brown.

Assuming that brown is ground, I measured +9V between orange and brown, and +1V between red and brown. Here's the funny thing: with and without the ignition on.

I noticed no pulsations over time, but for all I know it could be a millisecond long square wave electronic signal thing that drowns out in the noise fluctuation when measuring. I have no idea how these things work.

konigstiger

Axe Murder

Thank you!

I was just staring at that box and saw no burnt fuses. "Fused via wiper relay" should suggest that the relay contains the fuse functionality. Considering the oddball voltages I measured, the relay is my next suspect in line.

Axe Murder

Just for curiosity I removed and disassembled the wiper motor.
It was messed up. Full of corrosion, put together so that nothing could really be removed - all you could screw off was a lid, the rest riveted in place - and the rotor seized. A lot of WD40 did not help, that allowed me to slowly turn the rotor but with a lot of resistance.

So I ordered a new one. $90, problem solved. I hope.

Axe Murder

Well, I got the new motor, put it in place and it works.

Now - how do I get the blasted inner fairing back on to the door? Those hooks are not cooperating.

Was I supposed to remove the upper bits that go behind the brake light as well? How do I do that? I find none of those plastic rivets.

Axe Murder

Never mind, fixed it. By using my head. Literally.

Hooked in the lower end of the cover and held it with one hand. Grabbed the upper end with the other. Pushed with my head in the middle - and the cover bent just enough for the upper hooks to engage as well. Then I just had to reapply all the plastic rivets.

Case dismissed.