Porsche 79 targa - pwr windows not working (electrical) w/pics

supercarrera82 · 02-24-2009, 08:43 AM

I bought a 1979 porsche 911 sc targa with both the windowns not working, problem is eveytime I put a fuse in, it blows it instantly. The picture below shows the blue arrow that is getting 12 volts, however the bottom end of the fuse shown by the white arrow is geting no power (hence it blowing out). I tried following the wire but there is way too many thing going on around it to track it.

So I decided to take the driver door panel off, inside I found what I think is the window motor (please confirm) with the picture below, I put 2 white arrows showing the connections which were very very moldy with a bit of rust. My question is can it be the motor not working, if so why is there no power going to the other end of the fuse. And if the motor doesnt work will it not let the passenger window work either?? any ideas? thank a lot.

easelboy1 · easelboy1's Garage

Do you know if the PO replaced a window switch? The color coding of those wires leaves a bit to be desired. I ended up crossing a wire and blowing the fuse when I replaced a switch in my Targa. I can send photos of my wiring later in the day if it will help.

supercarrera82 · 02-24-2009, 09:01 AM

I myself replaced the window switch, but attached the same wires (same locations) to the new window switch, still got nothing. Could it be the wires are set up wrong on the window switch?

easelboy1 · easelboy1's Garage

I don't think that the switch wires would be different. It has been a few months since I did the work though I remember there being one connector turned on its side to allow for proper orientation; however, I do remember the OEM part as having numbered prongs and the new one did not....I had to go with several configurations to get it right in my mind as I was not fore-thoughtful enough to mark my wires as I removed them. Brown and Red wires looked the same on my car. Ultimately used a wiring diagram as a base line (which is in either Hayes or Bentley) and burned through a few fuses. Probably not a best practice!

I do also know that one crossed wire in the driver's side switch will kill the functionality of all window switches ....

jasonlee · 02-24-2009, 02:42 PM

The window switches are wired in series, so if 1 switch is not working or wired incorrectly neither window will work. Also cleaning those nasty looking connectors couldn't hurt either.

supercarrera82 · 02-25-2009, 05:28 PM

the window motor has 4 connection point and only 2 are connected, are they all suppose to be connected?? (see second pic)

j_mancini · 02-25-2009, 06:20 PM

Here are the wiring details for '77 (presume '79 is same) for power windows. If you keep blowing a fuse, something is grounding the circuit. Does it blow with the motor(s) disconnected? If so, that would suggest a fault in the motor. If not, you'd have to trace the wire and check for grounding - like a frayed or broken section. It's possible also the switch has failed internally, causing a ground.

Mysterytrain · 02-25-2009, 06:35 PM

I would test the motors individually and out of the circuit by applying 12 volts to the terminals. Also test reverse motion by flipping the test leads. Once, you are satisfied that both motors work or need to be replaced you can then start to troubleshoot the wiring. The switch schematic is in the following link:
Power Window Switch schematic

And this link in the wire harness schematic:

http://www.pelicanparts.com/911/911_Parts/Electrical/911_electrical_82SC_Part4-2.jpg

Basically, power is routed from pin 87 on the relay [when ignition is in the run position] to fuse 21 [25 amp]. Voltage is routed thru the fuse to the door via the red wire. If that wire is shorted to the body it will blow the fuse.
You can test the main harness for shorts by unplugging both door harnesses and doing a resistance ck with a meter..or installing a fuse and turn the ignition to the run position. If the fuse doesn't blow then install the drivers door harness and test again. Lastly, re-connect the passenger side harness. This might help to isolate where the short might be. The door harness plugs are located in the upper fender/door seam area, under the A pillars. They are visable from the outside of the car when the door is open.
Lastly, in the first picture. The white arrow is pointing to a red wire on the lower terminal on the fuse box..tell me that the brown wire is not connected there!

supercarrera82 · 02-26-2009, 09:20 AM

no the brown wire goes to the relay, thanks for your responses

the_captain · the_captain's Garage

Hi Guys,
I am brand new to the world of Porsche ownership and to this forum. I am not sure if this is the correct place to post this but I need a little help locating where to plug my wiring harness in to reinstall the power windows.

I am pretty sure that the car once had power windows but the previous owner removed them and installed manual window regulators. I wouldn't mind staying with them accept they don't actually roll the windows up all the way so that there is a 1" gap at the top of the windows, and the door panels I have for the car have the holes for the power window switches...

Anyway I was wondering if you could point me in the right direction as well as give me your opinion on the power windows and if I should just bite the bullet and purchase new window regulators that actually fit and new door panels to match.

Either way thank you for your help and have a great night.
JB

PS I had the most amazing ride from Ellijay Ga through the mountains and back roads back to Marietta the other day. Smiling ear to ear as I checked the rear view to make sure I hadn't picked up any fuzz....

These cars are amazing!!