I need to know if I can wire up relays to flip the polarity to run a power window motor. The car has factory wiring that works, but the windows are super slow going up. With a heavy jumper wire, they go pretty good, so it's a voltage issue. If I could run a heavy wire into the door, and use OEM wires to run relays, it would speed up the repair and not mess with all the factory wires or switches. This a late '70s model GM with the big windows, so send me a message if it's not allowed. I understand relays, just can get it in my mind how to flip power and ground.
It's not easy. You can use a DPDT relay to motor control direction, but you'd need two more relays to do the "on/off" for each direction. You probably need to fix the channels and lubricate all the moving parts to actually fix it. Finding replacement channels and fuzzies is difficult.
You could just find the source of the voltage drop and fix it. I'd start at the motor and measure the voltage with the window motor running. Then start tracing the wire back and find a connection and again measure the voltage with the window motor running. Keep moving toward the power source until you see the voltage rise (all tests are with the window motor running). The source of the problem is between the last low voltage reading and the first high voltage reading.
Fatigued wiring in the hinge area creating resistance has been the most common failure point in my experience, but cleaning and greasing the mechanisms sure helps things move easier
A few years back we did the power windows in my 55 bird, and the manuals in my buddy’s 56 Nomad. Channels, fuzzies, new rollers in the channels, and lubed everything. The reduction in effort in the manual windows and speed of my power ones was noticeable. Not to mention the rattles that disappeared. Well worth the effort. I think we got most of it from restoration specialties. The bird also used a relay system no longer available. The replacements are 2 relays as Jim described. All wired together and encapsulated in dip to waterproof them. Not an easy solution as he also said.
I had a mid 70s GM car recently, with manual windows, that I could barely move the drivers window up. After a little effort with cleaning, lubricating, and adjusting, it was easy to operate. I didn't do the p*** side, it wasn't as bad, but still took significant effort to make it go up. The clue that there's too much friction, is that it goes down OK, but not up. There's a spring in the regulator that helps it go up, and if there is too much friction, it can't do it's job.
As others have said, excessive friction can definitely cause this. Most late models with frameless gl*** and no vent windows don't have guide channels like older cars however, usually just one main channel that does most of the work. But those motors do wear out over time, so don't totally discount that either. The switches can degrade over time also. Checking voltage in/voltage out of the switch will tell you this. Motors are sized to the load, if the load increases they draw more current to perform the work, which may be why you're seeing voltage drop. It's not the cause, it's a symptom...
Thanks for the ideas, the car has been restored, I cleaned everything and greased where it was needed. It has new window trim in the doors and on the body, I even waxed the gl*** so they would slide easier. I was hoping to just pull the door panels and relay them with new power wires. Looks like I will live with it for a while while hunting down better motors and a switches. Switches are center console mounted, so theres a lot of wire getting to the motors. I close this up, don't want to be dealing with newer stuff. Joe
Basic reversing relay set-up diagram originally posted by Crazy Steve. Wire motor leads to relays 85 to power from existing switch. 86 to ground. An additional relay may be added to the 12V lead as a fail-safe; controlled thru diodes from the two switch wires.
Unless in the rewiring smaller wire was used (possible, if a typical aftermarket harness was used), that isn't the issue. The OEMs do cut wire sizes to the bone, but if everything is working properly that shouldn't be the problem. It's a symptom of the problem, the actual problem is something else.
Trombetta 12 Volt Reversing Polarity DC Contactor Part No. 214-1231-A61. Not cheap but designed for heavy use.
Also you may want to run a ground wire from the body to the door motor. Some times the hinges aren't the best grounds.
Unless he's got the oddball two-winding motors that GM used in the '60s, a separate ground isn't needed. You can identify those by the switch; those used three wires (hot in, up/down out), the reversing motor switches have four wires (hot/ground in, motor leads out).
I had a similar problem once with a volt drop on the power feed wire to the switch, traced it back to a corroded bulkhead connector. Water was finding it's way down the cowl and getting into the connector on the engine side. This was on a late seventies GM also. Good luck!
I had to do this on an OT Firebird I worked on. Two relays per door. Not that hard to do once you think it through. The original switches were bad and the ones we got were different design.
I didn't remember who had posted the drawing, otherwise I would have mentioned where it came from. Edited the post. Thinking about it now; it might of come up in a discussion that it would only take two relays to reverse the motor. Think I mentioned more than two relays as the equipment we had used more to cut the power ahead of the reversing relays.
The picture helps, took me a minute to figure out how it's working. This should do what I need it to do. Pretty sure its just a combination of weak switches, long old wires, older motors, and too many connections., on a '79 TA. Joe
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