1980 240D - Window motor internal fuse?

I have removed the window motor from the right front door. Using a continuity meter between the two wire leads, there is an obvious open circuit. The motor winding, commutator, and brushes are fine; they show continuity. There is a black, rectangular object inside the motor assembly, in electrical series with an inductor. The black box is less than an inch long, and says "9 017" on it. This black box fails to show any continuity between its two terminals. I think it's a blown fuse.

Can anyone concur that this is a fuse? Is there a chance I can buy such a fuse? Any tips on where to buy? I'd rather not buy the entire motor, as that seems unnecessarily expensive. If it's a blown fuse, it blew because someone I know was messing with the mechanism. I'm confident there is no major problem, here.

Any idea what the amperage of such a motor fuse would be? I might need to improvise.

Thanks, John

Reply to
John B
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No.. there is no user replaceble fuse in there... Try resoldering any joints you see there.

Reply to
Tiger

I am not familiar with this motor but on most P/W motors there is a non-replaceable automatic resetting circuit breaker. The amperage varies as does the shape and size. However anything is possible, just DON'T bypass it as this could cause more problems than you have now. Try to select one with just a little lower value than the fuse for the power windows.

Paul Paul's Auto Electric

Reply to
Paul

Well, I put my continuity meter right across the terminals of the black box, and it was "open." I just can't imagine what soldering would accomplish... What would that thing be, that's in series with a rather large inductor?

Reply to
John B

I concur on your advise for the amerage of any over-current protection device, within the motor assembly. It would be useless, unless it is less than the amperage rating of the upstream fuse. I suppose there might be other considerations, such as time-to-blow, etc. It makes complete sense that, in a quality automobile like a MB, there would be an auto-resetting circuit breaker in the motor assembly. Who would want to take the door apart, to replace a fuse?

I didn't ring out the other door windows, because I didn't want to take the door panels apart, for that purpose.

Shouldn't the two leads, coming out of the window motor assembly, show DC continuity, when tested on the bench? I have removed it from the car, entirely.

I have a beefy 13.8 VDC power supply, with which to bench-test the motor, but I'm afraid the motor's armature would jump out of the brush position if I did that. There's nothing holding the armature in position, axially. The brushes would then implode into the axle, shorting out, and ruining everything.

So doesn't a continuity test sound most appropriate?

Thanks, John

Reply to
John B

If I understand what you are saying the motor has been removed for an assembly which gives the shaft support at the opposite end of the brushes. If this is true you can't hardly do a bench test as is. If the shaft end is supported in some sort of bearing, and it were me, I'd simply apply 12-14v DC to the two terminals to see if the motor worked. If you have an open circuit then you can hardly do any more damage to the unit than now exists. It doesn't work now+...right? If that doesn't work I'd place the negative to a ground on the motor and the positive to each of the terminals to see if one takes it forward and the other backward. I don't think this is how it works since the reversing of polarity (I believe) takes place at the window switch itself. In this case my opinion would be, nothing ventured, nothing gained.

Reply to
The earnest one

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