Windows not working - wrong fuse blowing???

[Booney1golf]

Good evening. I have an 87 911 cab and the passenger window has been acting funny (I had to press the switch in various places that is on the drivers door to get the passenger window to go up or down). THis has went on for a little while so I thought the switch was going out. Then last week the Driver window quit working while it was half way down. Now neither window will work.

I looked at the fuses and the fuse closest to the drivers seat (1) was blown but on the lid it is marked fuel pump however the car still runs. I changed out the fuse and tried the windows (all three switches) and nothing happened. I looked at the fuse and it was blown again.

I got another fuse because I was going to try the passenger switch (window) only to see if it would work so to possibly point to a bad motor in the drivers door for the window. As I was putting the fuse in with the key off my thumb accidentally touched the copper/brass part of the fuse and it shocked/burned the heck out of my thumb.

I don't have a voltage meter and would not know how to use it if I had it.

Any suggestion or anything I can try without doing more damage to my car.

Thanks for reading this and responding if you have any thoughts or suggestions.

Daniel Womack (Booney1golf)
87 Porsche 911 Cab wide-body
98 BMW M Roadster
09 BMW 528I

[Booney1golf]

Bump

[DRACO A5OG]

check the seat motor connections, if the connectors are touching any metal, it will blow fuse #2 and disable the windows as well.

[geoz]

this may not be a massive help but I've had similar issues and I think the issue is likely a short somewhere in the system. i know how to use a voltmeter but still find going through the electrics on my car rather unpleasant, particularly after many people in the past 25 years seem to have found it necessary to install extra wiring that is hard to trace - and of course cut through factory wiring as well.

a good place to start would be to check the switches since you said they were hit & miss. then get 12v to the motors and see if the work. next you might check if the cables coming from the door - those seem to be prone to wear out over time. after that it might get a bit more difficult.

[Porboynz]

+1 on all this advice then apply normal fault finding process of disconnecting half the problem and retesting, that way you know which half the problem lies in. (Unless there are 2 faults, but lets not go there)

You instictively started doing this when you tried the new fuse. Be reassured it was not a shock at 12V, probably a burn, which is interesting if the key was off.

Why don't you mark the wires with small dots of paint or whatever and then photograph each switch. Then remove all the wires from the the drivers window switch, then retest for fuse blowing, then take the wires off the passenger switch, then the passenger side switch on the drivers door. Might take a few fuses but you should isolate the fault area fairly quickly. Multimeters are cheap and fairly easy to master, seek the help of someone who owns one to show you.

[86 911 Targa]

Originally Posted by Booney1golf

Good evening. I have an 87 911 cab and the passenger window has been acting funny (I had to press the switch in various places that is on the drivers door to get the passenger window to go up or down). THis has went on for a little while so I thought the switch was going out. Then last week the Driver window quit working while it was half way down. Now neither window will work.

I looked at the fuses and the fuse closest to the drivers seat (1) was blown but on the lid it is marked fuel pump however the car still runs. I changed out the fuse and tried the windows (all three switches) and nothing happened. I looked at the fuse and it was blown again.

I got another fuse because I was going to try the passenger switch (window) only to see if it would work so to possibly point to a bad motor in the drivers door for the window. As I was putting the fuse in with the key off my thumb accidentally touched the copper/brass part of the fuse and it shocked/burned the heck out of my thumb.

I don't have a voltage meter and would not know how to use it if I had it.

Any suggestion or anything I can try without doing more damage to my car.

Thanks for reading this and responding if you have any thoughts or suggestions.

Daniel Womack (Booney1golf)
87 Porsche 911 Cab wide-body
98 BMW M Roadster
09 BMW 528I

The Fuel Pump fuse is #6 from the driver's seat.

Fuse #1 is for Power Windows, Seat Heating, Sunroof.

If you turned the key on after you opened the door, the P/W relay logic
applied voltage to the P/W relay.

I would pull the black wire from the top of fuse #1, then re-insert another
25A fuse.

If the fuse does not blow, then the short is fault isolated to either the
P/W relay, motor, or associated wiring to the switches.

If it still blows, then you have an issue with the seat or, sunroof circuit.

Also, one of the problems might be a loose hot wire inside the
door at the window switch, a defective switch,
or a short in the door>door hinge post harness.

If you pull the window switches, do it slowly and carefully without a fuse,
and check the connections.

Try to get some help from another local P-Car owner.

This is as far as I can take you, maybe someone else will chime in.

Good luck,

Gerry

[Joe Bob]

Window fuses are 25amp BTW....ask me how I know.

[Booney1golf]

Thanks to each of you for the responses. I will make time this weekend to try some of these.

Thanks again,

Daniel Womack (Booney1golf)
87 Porsche 911 Widebody Cab
98 BMW M Roadster
09 BMW 528I

[scarceller]

If you just put the fuse in and it blows without touching any window switches you have a short. It could be in one of the motors or the switches.

When working as designed both the '-' and '+' wires (both wires) going to the motor have 12vdc on them. What the switches do is simply remove 12vdc from one of the wires and ground it to make the motor go in one direction. Then if you flip the switch the other way it grounds the opposite wire. You really need the schematic to understand how they work.

Because the motors always have 12vdc to both wires going into the motor any malfunction in the internal wiring of the motor can easily result in one of the wires being shorted to the motor case, once this happens fuse blows.

Here's how I'd try to narrow this down:
- Disconnecting the motors is a pain
- But pulling the switches out is not so bad
- Remove the passenger side switch and then also remove the drivers side switch that controls the passenger side window.
- Your simply removing both switches that control the passenger side window.
- Leave the drivers window switch in place.

Now try to put back the fuse, does it still blow immediately? If not does the drivers window work? If it does you know you have a problem only with passenger side window.

If the fuse blows then proceed to also remove the drivers window switch so you have all 3 switches removed and try again.

You need to pinpoint what window is causing the issue and then we can go from here.

If you remove all 3 switches and the fuse still blows then you need to start looking at the power seat circuit.

I think you have 2 problems going on at the sametime. The first issues is that the passenger side window already had issues and you needed to push on the switch and tinker with it for the window to work. It's common for these 30 year old switches to fail just as you describe and usually odds are the passenger side window has this issue since it has 2 switches. Fixing this is as easy as replacing the switches.

But I think something else occurred besides the finicky switch issue you described.

My bet is you have a bad motor or a switch that internally shorted, that's why if you remove all 3 switches it also removes the motors and if the fuse does not blow then you know it's a switch or a motor and we can start testing further from here.

[KTL]

Originally Posted by DRACO A5OG

check the seat motor connections, if the connectors are touching any metal, it will blow fuse #2 and disable the windows as well.

Big thanks to you for posting this tip. I recently installed some junky seats for temporary use in my '87 and coincidentally found the windows didn't work. Car had been down for the count for so long, I figured I had done something else to disable the windows (had been messing with the switches and door panels not too long ago) and would have to do some hunting to find out what I disturbed. Battery was also completely discharging.

Well I pulled the seat, disconnected the power plug, put a new fuse in the fuse panel and yippee I have working windowage again! Thanks man

[fitchesbass]

For what it's worth in my car's problems:

I had a similar issue and found the female connectors on the back of the switches were touching or close to touching. I don't know if the wires / connectors were redone by a previous owner, but I took them apart, cleaned them up, and made sure they were all insulated from each but wrap each connectors with a piece of electrical tape. - solve my shorting problems with the windows.

My car is a coupe, so perhaps its different. But the the fuses I always had to mess with with regards to the windows are in the front trunk.