Your help in sorting out a power window operational issue on a 57 C1 will be helpful. Here is some background:
- Car had frame off restoration in 2011 for the Mecum Collection; working around the car they seem to have done a decent job on everything (except the tranny - they didn't set it up correctly, but that has been fixed this year). In some cases they left original items in place, in others they put in new material.
- The car has very, very few miles since restored; I've driven more in the last 6 months than the previous 10 years.
- Driver's and passenger's door switches and connectors are original.
- Motors appear to be new from restoration.

Issue: The windows operate intermittently. Sometimes both work, other times neither work. Here are the things I have checked:
- Circuit breaker on firewall appears to provide voltage on the output side.
- There is 12V potential between the red connector (power in) and all 4 up/down connectors for the 2 windows.
- The driver's door switch correctly connects the red (central) pin to the up/down pins for each window.
- When the driver's side switch is re-inserted into the connector, nothing happens (at this moment) when the switch is operated.
- I have not pulled the passenger door panel/switch off yet.

I can't seem to nail down the source of the intermittent operation. If the circuit breaker was acting up I wouldn't have power at the driver's side connector. I'd appreciate your collective advice on where I need to look to find this gremlin.

Thanks!! Glen

 

I would get want to direct jump the motors verify operation. Then jump at the relay. Then jump across the breaker. See if they run without binding. I would want to see that all the wiring and motors are in good shape no sign of overheating. I did window felts recently and there is a surprising amount of drag. My guess is your system is overheating someplace.

 

I'm familiar with the circuit breaker, but couldn't find any location reference for the relay. Where is it located? If between the motor and switch, that definitely could be the source of issue. However, I found a drawn wiring diagram elsewhere in the Forum that suggests it is between the circuit breaker and switches. If there could it be limiting current flow? Greatly appreciate the insight John!

 

On my '62 the switches were problematical. Contacts get dirty and worn. Concentrate your efforts here.

 

DOH. no relay. All that heavy current runs through the switches. They can get coroded and make a thermal overload but the comment s for direct jumping to verify operation apply. The system should have relays!

 

Yup, my experience exactly.

 

I’ve had issues too - if I move the windows by hand (help them up) - while hitting the switch, - they seem to work ok…. I’ll bet I need to install some relays too. If anyone comes up with a wiring diagram on where these should be….. ???
Doors panels are off right now - good time to retrofit.

thanks

 

I had the same thing; had to help the windows up. Took the motors out (there is a special way to cheat doing this to make it easy) disassembled them and found the commutators were all gummed up with decades of grease film, I presume. Cleaned them off as well as the brushes and they worked like new (not that I know what new ones work like).

 

I guess I could check them - but Mine were “New” about 8 years ago. Have sat in the doors forever, and didn’t get used much, as my car didn’t have a top.
So, now that I’m working to complete the Airconditioning system - so I can Install the hardtop, the windows might actually get some excercise.

 

Will try to assist windows up while flipping switches. I jumped the 5 hole connector but nothing. Unless all wires are intermittently broken, jumping at the connector to 12VDC should work. I think I'll re-try but with an amp meter in line to gauge load. Will also measure potential to ground while activating switches to see if it drops due to a partial short. Worse comes to worse I'll work to get the windows up so I can pull each motor and benchtop them. Sounds like a few hours of work. Will be back with results, good or bad. Thanks

 

Just remember that removing the switch from the circuit also removes the ground so '1' jumper to 12 volts won't do it without an additional jumper to ground.

 

First of all can you run the motors with direct power to ground application?

 

Update:
I determined that 12VDC is getting to the correct motor leads in the drivers door when the switch is engaged up or down. The switch had been working fine, but the entire mechanism was loose so I took it apart, polished the contacts, and tightened up the entire switch assembly. Good PM.

During measurement of power to leads I wasn't sure where to attach my tester ground lead, so I hooked it to the steering column while measuring applied voltage at each of the motor connectors in the door (through the front access panel opening). The 12VDC measured stayed up at battery level suggesting no short. When I applied the ground lead of my tester to the motor case and the other lead to either motor leads, no 12VDC was measure when the switch was actuated.

That got me thinking. There is power to each motor lead but the motors don't run. I checked a nice schematic that was sent to me (drawn by Justplainwacky - nice job!) and it showed the ground for the window motors runs back to a spade lug which is grounded to the brake pedal. I haven't crawled under the dash (it's late and 95F in the garage) to see if that is the case, but has anyone found faulty window motor operation tied to a bad ground connection under the dash? This would make sense because unless the motor case is electrically isolated from the ground side of the windings (not my experience), the motor case should be a good ground to measure potential at the leads. So measurements suggest power is getting to the up/down motor leads, but the circuit is not complete somewhere.

 

IIRC the motor case isn't necessarily grounded to anything. The switch just reverses the current. You should have one test lead to each of the wires on the plug and look for reversal of voltage. The wires going to the switch should have a main ground somewhere.

 

I want to thank everyone for the ideas and comments as I sought out the electrical gremlin hiding in the car. Found the little bugger today. Following up on my thoughts above, I took a length of wire, stripped on both ends, and ground one end to the frame. The other I touched to the driver's door motor case, and ta da, the windows worked. That meant the system ground for the power windows was not grounded. Taking a cue from the diagram received earlier this year, I got under the dash and looked for a black wire coming from the wire bundle coming from the door, and there it was on top of the column bracket. Grabbing it, the connector came up attached to nothing! So that explained why there was a problem and why it was intermittent. Sometimes it grounded out and the windows worked, sometimes not. Just another gift from the guys who restored this car 10 years ago and didn't quite wrap it up. Maybe it was a busy day. Either way, re-attached it to frame ground and both windows work fine. At least I didn't have to pull the motors starting with the windows down.

Lesson learned: If the problem isn't where it should be, look for the problem where it shouldn't be and leave no stone unturned. Again, thanks for the input folks.

 

JF in MI

Could you please elaborate on the easy method for removing/testing the window motors? I believe I need to remove the regulators, and understand the motors are part of them.

Thanks!
Bill

 

I can't help you if it is a C2 because I've never done one. If it is a C1 this thread may help...

https://www.corvetteforum.com/forums...-followup.html

I've also had issues with old switches where the contacts were pretty used up (burned) from age.

 

Hi Bill,

Removing the regulator / motor assembly is somewhat of a PITA. There are several posts on Forum describing the process and it's easier if the windows start up as now they are out of the way.

You're on the right track to test first before tearing into things. I list how I diagnosed my motor function above. You need to pull the door panel off to get to the connector block that plugs into the door panel switches. From there a series of jumper tests will allow you to determine what's up. As I learned, the motors didn't work because I had an intermittant groung connection under the dash (there is no grounding in the doors required to complete the 12VDC circuit.).

Glen

 

Thank you guys for the quick response!
The windows are currently in the down position. I used a Power Probe, and the windows will "bump" up and down, but will not go anymore than just, what I'd call, an acknowledgment of receiving power. I'm assuming unbolting and removing the motors make it easier to remove the regulators. Is that correct?
Also, I guess I'll have to remove the window glass, as well.