Author Topic: Power window problem 79 Trans Am  (Read 8125 times)

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Offline 7t9ta

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Power window problem 79 Trans Am
« on: June 08, 2006, 07:41:14 PM »
The passenger power window on my 79 trans am stopped working. when I take the motor out and ground it against the door it works. When I put it back together (twice) it goes down & up once and quits again. It clicks when I move the switch. The window moves fairly easily by hand.  Any thoughts what I should try next? Is there any way to test the motor? Thanks

Offline ta78w72

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Power window problem 79 Trans Am
« Reply #1 on: June 08, 2006, 09:33:41 PM »
Since you already have the door panel off, try attaching a ground wire to one of the motor fasteners.  Run the wire through the boot and find a ground spot somewhere on the dash frame or firewall.  There is no ground wire for the power windows.  The motor is grounded to the door via the fasteners and the door to the body of the car via the hinges.  A really poor design because those areas can rust.  So, if you run a new ground wire, you can eliminate a bad ground.  That may not be your problem though.  You should measure the voltage at the motor and switch.  

They had a thread on this on that "other" forum which shall remain nameless!  The summary of the post was that the design was poor, not properly grounded, and there was too much current drawn through the swtich which causes them to burn up.  The poster recommended a new circuit design which took the load off the switch and enhanced the grounding.  I took his narrative and drew up a crude wiring diagram.  Essentially, you bring in a new power supply line from the battery and hook it up to four relays, one for drivers up, drivers down, passenger up and passenger down.  The switch then controls the relay and the relay takes the load.  Each relay is grounded as well as both motors.  This takes the pressure off the switch and provides sufficient power to the motor to power the windows up and down.  If you want the diagram and narrative, send me an email and I'll send it to you.  The poster did a great job in describing the circuit....so good that an accountant could take his words and draw a picture.

Sorry for the long post, but this information may be helpful in the long run.

Offline Banditboy21

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Power window problem 79 Trans Am
« Reply #2 on: June 11, 2006, 01:35:52 PM »
can u send me the circuit diagram

Offline ta78w72

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Power window problem 79 Trans Am
« Reply #3 on: June 11, 2006, 04:15:09 PM »
Quote from: Banditboy21
can u send me the circuit diagram

Sure, but I need your email address.  You can PM me with it.

Offline 7t9ta

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Power window problem 79 Trans Am
« Reply #4 on: June 21, 2006, 12:22:59 PM »
Update - I added a ground wire from the lug on the motor to a regulator bolt in the door, that solved the problem. Ta78w72, thanks for the diagram, I may go that route this winter to avoid future problems.

Offline ta78w72

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Power window problem 79 Trans Am
« Reply #5 on: June 21, 2006, 06:07:33 PM »
That's great news!

By the way, that new wiring structure is suppose to take all the current off the switch and avoid burning out the wires.  I haven't done it on my T/A yet.  I currently have roll up windows.  But I have everything I need to convert my car to power door locks and windows.