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Electrical question.....(not a tractor)

B

banjoman09

Well-known Member
I always try to play by the rules here...but let me stray one time please....; Im rebuilding a 1980 Corvette(C3) and replacing the window motors...I can make the new motors go up and down in the door with a battery charger hooked to the motor BUT when I plug on the wire and use the switch it does nothing! Take plug off motor and use testlight and the plug lights when using the switch....it is loosing juice when it plugs on the motor- makes NO sense to me.....any takers?
 
I agree, putting the light into the circuit when the motor is attached will show the circuit is not being supplied with enough current. Possible fuse contacts, or a bad Broken wire at the door hinge. Don't try the motor more than a few seconds, the bad connection could get very hot. Jim
 
I'm pretty sure that window regulator motor gets its ground through the case. Try putting a temporary ground from the motor case (not on a painted part) to a good ground point and see if they work. Just a wire with alligator clips or a jumper cable will work for providing the temporary ground.
 
When diagnosing an electrical problem, it's best to check voltage with the load (the motor in this case) in the circuit. The resistance of your test light is much higher than the resistance of the motor windings, so it's likely to give a false reading if the motor is disconnected. If the switch is bad, it may still be able to light up your tester.

The few door motors I've messed with had two windings and a common return (ground). As others have said, you also need to be sure the motor is properly grounded.
 
I'm in the camp with a bad ground, bad switch or connection as a possibility. It could be a connection or splice even if it appears okay to the eye. If there's a voltage drop caused by a bad resistive ground or connection etc. IT (V = I x R) ONLY HAPPENS WHEN CURRENT IS DRAWN so stick a volt meter on the motor when you try operation....

John T
 
(quoted from post at 21:28:35 10/17/20) I always try to play by the rules here...but let me stray one time please....; Im rebuilding a 1980 Corvette(C3) and replacing the window motors...I can make the new motors go up and down in the door with a battery charger hooked to the motor BUT when I plug on the wire and use the switch it does nothing! Take plug off motor and use testlight and the plug lights when using the switch....it is loosing juice when it plugs on the motor- makes NO sense to me.....any takers?
Click to expand...

You could use various tools and testers but you already have everything you need to track down your problem.

You had your battery charger hooked to the motor and it worked when you supplied power to the terminals.

Move the ground from your battery charger to a good ground point not on the door and see if it still works, if it does ground circuit is good, if it doesn't you have found your problem.

If the above did not solve the problem then move onto the switches.
Simple 3 wire circuit
Power comes in on pink wire then goes out to motor through one or the other for up and the other for down.
Leave the ground where it was from the previous test and apply battery charger power to the other 2 wires (one at a time) at the switch plug terminals and see it the motor responds, if it does on both then you have confirmed the wiring from the switch to the motor is good.

Next would be the switches
Supply 12 volt from your charger to the pink wire with everything else connected. Both windows should now function up and down, if they do not then you have a switch problem.

If switches test OK then move on to power supply, check the little tin can breaker in the fuse box, if you do not have a spare you can temporarily substitute a fuse of the same value for test purposes, if the windows now work then the breaker is bad.

All of the above tests are based on connecters already being checked for cleanliness and tightness.

If they still are not working then supply your charger power right to the breaker terminal in the fuse box, if they work now but not without the charger connected then it is time to check the back of the fuse box for loose or burnt connections.
 
Thank you for this; I do believe it is a 2-wire connector to the window motor; guessing one is "up" and one is "down. No the old
motors did NOT work but now thinking they were good - is my fault for condemning them as the problem is elsewhere.
 
ok will do.... I know when I put my test light probe in the plug and hit the switch....it does not light. I was thinking bad ground on the door but the door seems to be grounded to the car ok- must be on up the line. Thanks
 
You got it, if there's low voltage when you place a load on the circuit there's EITHER a bad/loose/resistive V = I x R voltage drop up the line (switch or ground or connection) or else the motor itself has a serious problem or short ?????? Hard to say sitting here grrrrrrrr

John T
 

Check it...

I would hook up one of my load testers to the circuit...

4 amps car headlamp bulb.



mvphoto63542.jpg


2 amp 1157 taillight bulb




mvphoto63543.jpg


Its as simple as it gets other than wheres the ground come from I have read its internal to the motor so the motor body has to be grounded to the steel part of the body... How does it get there I don't see a dedicated ground in the harness I speck its travels thru the door hinge... A quick test would be to run a ground from the negative post of the battery to the window motor shell...

Vette's and their grounds : ( When I work on those I run my own ; )
 
No,

The motors are not grounded, that is handled in the switches, as they reverse polarity.

The master switch isolates the ground on a lot of cars.
 
Where are you clipping the ground on the test light when you test? To the window motor or to a ground elsewhere? If test light has a good ground, the light should light up on each contact of the pigtail when the switch is toggled accordingly. Do like Hobo says and start with a long jumper from the battery to the motor's frame or mount. If all else is right, the motor should run when the switch moved to either position with the pigtail attached to the motor contacts.

The schematic shows the motor grounded to the car frame, the way I read it. Not through the pigtail. Someone has mentioned that motor has two sets of windings for up and down. Let us know what you find when you get a chance.

Garry
 

If you want a fun one tell me where the ground is at for a 68 vette wiper motor... Its not wired with a ground wire at the switch and the wiper motor is mounted to a fiberglass firewall with no dedicated ground wire at all...
 
If you want a fun one tell me where the ground is at for a 68 vette wiper motor... Its not wired with a ground wire at the switch and the wiper motor is mounted to a fiberglass firewall with no dedicated ground wire at all...
Click to expand...

That's easy. It grounds through the black wire off the wiper motor harness through the same ground point as the blower motor.
 

The wiper switch fits into a metal gauge cluster, the gauge cluster does not have a ground it get its ground from touching the metal console/sifter/plate/cover that does have a ground wire screwed to it... They just butt together what a concept only on a corvette...

Until you ground the dash wiper switch BASE/HOUSING the wipers will not work... I was making sure everything would work on this one before I put the interior back into it the wipers fraught me for a week till I found this out...

OK Y'all may be right on the motor my bad it will not run on the car unless the wiper switch base is grounded...



mvphoto63601.jpg
 
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