power window fuse

[Rjackel944]

My power window fuse keeps getting burned out and I'm wondering what could cause this? They only work for a couple uses..
Now I realize I've only been using spare used 16 amp fuses that I got laying around, but so are all my other ones.

Thanks,
-Ryan

[kfray]

My 1987 944 NA has a 30 AMP fuse for the Power windows.

[mikepellegrini]

For the early cars, the power windows is supposed to be a 16 amp fuse - I'd guess the late cars are the same. 13.0 Electrical

The electrical circuits are overengineered so there's a certain safety factor built in, but I'd really worry about running a 30 amp fuse in a circuit designed for a 16 amp fuse.

If your car is blowing 16 amp fuses, it suggests that there's a short. Going to a higher apmerage fuse is just asking for trouble.

[Rjackel944]

How would I go about finding a short? My dads an electrician so he can help me but where do I look first?

Thanks!
-Ryan

[mikepellegrini]

If it was me, I'd take the window switches out (and unplug them) and use a continuity tester to see if you can isolate which circuit/door the short is in.

You dad would have a continuity tester (a VOM) - it buzzes when you complete a circuit. To test the circuits, you'd ground one lead of the VOM then touch each of the positive wires with the other lead in turn to find out which circuit is shorted.

In 944's, the ground wires are almost always brown - so the positive wires will be any color except brown.

Hopefully, you'll be able to isolate which window/door the short's in.

If you can't figure out which door, then you really have to tear both of them apart and again, using the VOM, start wiggling wires and see if you can find the short.

Does the fuse always blow at a certain time/event, or is is completely random? Do you have to be operating the window for it to blow? If so, which window (or both)?

[Rjackel944]

Sounds like a good place to start! Well lets see. I can use the windows a couple times and then i go out after a day or so and then they no longer work.

[Vicious]

that test would work, but you missed one point. his windows work but blow the fuse after a few uses, this means there is no problem with continuity ib the circuit there is a problem with resistance. check all your ground wires as its the most likely cause of increased resistance. and tell your dad to perform a voltage drop test to determine where the resistance is higher at.