Power Window circuit breaker- Testing

[2761377]

so my '91 318i keeps popping fuse 17, for power windows. electrics are definitely my weakness; after research I can't see any other reason than a dead circuit breaker.

does that even happen? where a breaker fails to trip and sends overload down the line?

how to test?

the relay operates properly and shows no resistance when the circuit is complete.

thanks

[bradnic]

are you talking about the window switch with the red border around it? afaik it's just a cutoff switch, not a circuit breaker. are you're blowing fuses (a) immediately, (b) whenever you hit a window switch or (c) only when you're holding the button down and the window is all the way up or down?

(a) would be a short to ground - a frayed wire somewhere on the power side of the circuit
(b) would be a short on the switch side of the circuit (e.g. after the switch but before the window motor
(c) is probably a bad motor

good look

[Das Delfin]

^ it's a circuit breaker. It's meant to sense when your arm is caught in the window by breaking the circuit when the motor draws more current than normal (ie it has to work harder to close the window with your arm in the way)

I've had a bad wiper motor blow a fuse whenever the wipers were used.

[bradnic]

then we're at (c) window motor drawing too much current. that could be something wrong with the motor or a mechanical obstruction, window tracks needing some lube etc.

I'd try hitting the window buttons one at a time see if there's a specific one that pops the fuse. probably the driver window though lol.

[2761377]

^^^ yeah I think that must be the issue. there's nothing else on the circuit so somehow an overload from window operation is making it past the circuit breaker.

my 18 y/o son is driving the car, not me. so far, the only thing he can tell me is windows stopped working. he has instructions to pay closer attention.

thanks all

[george graves]

Unless your "circuit breaker" has a red surround on it, it's not a circuit breaker. It's a cut off child switch. And even then, it doesn't really work. Just FYI.

I've taken apart them, and tested both the "circuit breaker" types, and they are only there to trip if you lean on the switch and overload load the motors for along time in an up or down position. You can delete them if you want.

[2761377]

Unless your "circuit breaker" has a red surround on it, it's not a circuit breaker. It's a cut off child switch. And even then, it doesn't really work. Just FYI.

I've taken apart them, and tested both the "circuit breaker" types, and they are only there to trip if you lean on the switch and overload load the motors for along time in an up or down position. You can delete them if you want.

this is the part I'm talking about- pn 61311369375



so what you're saying is that this component does not protect fuse 17. just to be clear.

thanks

[Das Delfin]

It works the other way. Fuse 17 protects the wiring. So if your circuit breaker was stuck closed and caused the fuse to blow instead of the breaker you still have a problem with something drawing too much current. See if you can isolate which window caused the fuse to blow.

[george graves]

so what you're saying is that this component does not protect fuse 17. just to be clear.
thanks

I'm not sure what you are asking. I'd kindly ask that what you know now, re-ask your question - or ask a new one. I'm a bit lost of how to help.

[2761377]

It works the other way. Fuse 17 protects the wiring. So if your circuit breaker was stuck closed and caused the fuse to blow instead of the breaker you still have a problem with something drawing too much current. See if you can isolate which window caused the fuse to blow.

Thanks for your reply. scary for you, I think you understand me. ;) if that component is bad, I'd like to replace it. the cause of the overload is a different question.

my original question was 1st is it even possible for it to fail closed?, and 2nd how to test it. I guess I could roll up a window on my arm until the breaker trips, the fuse pops or it cuts it off. whichever comes first.