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I just pulled the window motor from my drivers side 928S '84 euro door. There is no continuity on the motor and putting 12 volt on it does nothing. The continuity is broken in a big piece of black plastic. I tried to illustrate it on the photos below. There is no continuity between A and B and no continuity between C and D which are the two points that stick out of the bottom of black piece of plastic. Is that perhaps a Fuse? Also, what happens if I remove the Fuse and just connect C and D? Will my car be a ball of fire?
That black box ihas a thermal strip inside that may be why there is no continuity. It is removable and you can get inside it. I have done it before and it saved me a lot of money not buying a new motor assy. You got numerous things going on there from the rusty drive gear to everything needing cleaning. The motors are very dependable. You can see they run in both directions depending which side gets the volts. check in search on the forum.
Okay, interesting. Yeah I can solder the two points of the bottom and remove it. So, there is a thermal strip you say? Is that the same as a fuse? And is it supposed to not show conductivity?
I was thinking about just soldering the two points that go inside the black thing together with a little wire. Or that a really bad idea.
the thermal strip is there to prevent the wires from getting smoked if the window is not moving and the switch is being pressed,
if you cant fix this one,
then buy a used one from 928 INTL,
it looks like its about time for that to happen anyway.
I dont know I never tried to take out a safety part to see if the wire harness will not melt .
NOTE its quite common for window switches to sometimes stick in the up or down position due to heating of the switch quadrant,
this could then have a switch activated while your driving then if you smell/see smoke turn off the key.
My suggestion fix the motor properly their are plenty of used parts available also new parts as well
The 'thermal strip' is basically a self-resetting circuit breaker.
If it gets hot, it opens the circuit to prevent other stuff getting really hot (like 'on fire' hot).
When the circuit is broken, the strip will cool of and restore continuity. If the switch is stuck, the cycle will repeat itself. If it was just an idiot holding the switch for too long (or maybe a dog holding the button down), then it will go back to normal.
I would very strongly suggest against bypassing or deleting it.
Based on my experience a) it's a thermal fuse, not a breaker, and b) I have taken apart one motor where it was bypassed and the innards had pretty much melted away. YMMV!
I recall sitting in traffic one day, taking a fellow owner home when his clinic day was extended as we needed extra parts. Hot day, L.A. traffic stop-and-creep-and-stop. The volt gauge was cycling down regularly, then relaxing. AC at full tilt and engine essentially at idle the whole time, the recovery point was getting lower. Faint clicking in the door... Window switch was indeed stuck, and that thermal overload was cycling to protect the motor. Removed and cleaned the window switch. Problem solved.
The fuses in the CE panel are there to protect the wiring, not the end-use device. While there are lots of fuses in the CE panel, not all circuits are adequately protected in my opinion. Folks with melted harness sections can chime in here. Anyway, the potential is there to draw 20 amps in a single locked window motor, and that will quickly melt the motor insulation, adding more heat, and it only gets worse. It seems we too often resort to bypassing safety systems in the cars when they work, rather than fixing the underlying problem. Here's a case where a protective device has more than done its job. Fortunately there are good sources for the pieces needed to fix this one. Make sure that the motor itself isn't damaged, else you'll want a replacement assembly.
Okay, interesting. Yeah I can solder the two points of the bottom and remove it. So, there is a thermal strip you say? Is that the same as a fuse? And is it supposed to not show conductivity?
I was thinking about just soldering the two points that go inside the black thing together with a little wire. Or that a really bad idea.
Hi there, I'm back. I managed to find a reasonably priced complete replacement. 75 gbp for a second hand motor plus scissor thing.
I just wanted to say thank you for your tips you guys. Always very helpful. I can't say it enough, this is a great forum. Ehm, and here's video of the window working again:
06-10-2018, 01:46 PM
Window motor broken
