Update: 1980 CV Electrical Issue

banjoman09 · Oct 28, 2020

Finally went back to this project as I need my neighbor to come help when we both find time; Ill post one more time then not bother any of you with this...not easy to diagnose a problem sometimes without being infront of it; so....On my door motors that I replaced on my Vette...(that still dont work) pull plug off window door motor and check with test light that is grounded to the door- push switch and lights test light- both directions; put plug back on motor and notta...nothing...no workie; used volt meter and it reads 11.5V on each wire when push window switch; BUT when I plug the wire plug back on the motor and probe back of plug and hit switch....no light....no volts...nothing...its like the juice "goes away" when you put the plug on the motor and hit the switch! I traced wires to fuse box...cannot find a circuit breaker light the diagram says it has...all fusses check good....very strange. I really think the ground circuit is good otherwise the test light would not light when i check the plug. Help?

RogerinIowa · Oct 28, 2020

Door motors pull amps, test lights not so much.
Will motors work directly off of separate battery and wiring?
Could be broken wire with maybe only one strand intact. Could be on hot side or ground...

Donaldinky · Oct 28, 2020

Need to see how many amp.the motor pulling.
See it the motor is running hook 12 volts to the motor. One side to a ground. Could be bad motor. New don't mean anything. Bad connection or bad wire. Could be a bad wire when the door opens and close. Put a wire from your neg side of the batterie. Easy ground check. Check all your connections where they plug into. Some under dash board. Check plugs at the fire wall. Clean and dielectric grease.

Janicholson · Oct 28, 2020

Bare a small chunk of the wire to the motor (before the connector). Assure yourself that the wire will light the teat light when it is not plugged into the motor, and the switch is pushed.
Then connect the motor and touch that bare patch and try it. If the light does not light it is supply side issues. If it does light, and the motor does not operate, it is likely a faulty ground at the the window switch. Remember the switch provides both the juice, and the ground to opposite wires going to the motor. If the switch ground is bad, no go. Jim

gab · Oct 28, 2020

It's been awhile but I think the two wires to the motor switch polarity when switched up/dn.

banjoman09 · Oct 28, 2020

aahhhh....did not realize that...thanks.

banjoman09 · Oct 28, 2020

Yes I replaced both motors thinking they were bad...my mistake but oh well...they both work when powered with my battery charger so I know they are good motors....VM reads 11.5v when I push switch...I did check amps when switch is pushed but I dont think that tells us anything..it read .01 amps.....that is the plug when not connected to motor.

Jeff NWOH · Oct 28, 2020

What does your meter read checking voltage at the battery? 12.6 ish? If you're only getting 11.5 at the window motor connector with no load, you have a problem. It should be basically the same as battery voltage. I'd guess you have a sketchy connection somewhere. It can carry the carry enough current to light your light, but not run the window motor.

Your checking voltage with the motor connected and getting nothing basically confirms it. Since neither motor works, I'd guess the problem lies prior to the power splitting to feed each door.

My $.02 worth....

david from mo · Oct 28, 2020

You do not have enough amps or a bad ground! Hobo gave you the wiring for your motors in your other post and the way to test it with a headlamp bulb. Find your 30 amp breaker and test with a headlamp. These motors do not swap hot and ground like most do .

Steve@Advance · Oct 28, 2020

As said, the switch provides both power and ground to the motor. There is no motor case ground.

Power window problems are very commonly in the switch, usually the drivers door switch as it gets the most use and is the more complex one.

A wiring diagram would be very helpful but hard to find. have you searched any Corvette forums? Maybe find a diagram or could be a common problem with that model.

I would start looking at the drivers side switch. There has to be a positive and ground wire to the switch. Determining which wire is the hard part.

Once you determine the main power wires, check for 12v ACROSS those 2 wires while trying to operate a window (performing a load test). If you don't have power there, there is a bad connection to the switch. If good power, chances are it's the switch.

Sometimes you can ease them apart and clean the contacts.

david from mo · Oct 28, 2020

this system unlike most does not swap power and ground

MarkB_MI · Oct 29, 2020

Well, there's a bad connection somewhere causing a voltage drop. It could be both switches are bad. (Or both relays, if it has relays). Or the circuit breaker is bad. Or there's a corroded connector. You need to check the voltage further upstream. There is a circuit breaker somewhere for the windows; you just have to find it. Verify the voltage is good there under load and then work your way downstream.

UncleTom · Oct 29, 2020

I would like to hear your follow up on what you found that fixed it.

gab · Oct 29, 2020

From my unofficial library. This is a couple years off but still the same body style.

banjoman09 · Oct 29, 2020

awesome and thanks to so many of you...yes this helps a whole lot and will go from here and let you all know hopefully in a few days. Thanks again!

GarryinNC · Oct 29, 2020

Banjoman, Look at the schematic and text from shop manual published in this thread. The motor's cases are grounded to the vehicle frame and the motors themselves have two sets of windings, one for up and the other for down. Working the window switch puts 12 volts one set of windings or the other. Do like has been recommended and first run a dedicated ground from the battery negative terminal to somewhere on the motor's case/housing. Hook the switch pigtail to the motor and try it. If the motor works, you have a ground problem. If it does not work, you do not have an adequate supply of power to the motor. In that case, run a wire straight from the battery plus terminal and touch it to one motor terminal at a time. It should run. This proves that the motor is good and that the problem is in the vehicle circuitry.

Let us know what happens.

Hobo,NC · Oct 30, 2020

Nice post Gab...

The moral of the story buy a manual for your make and model... While at it get a dedicated manual for the headlights sooner are later he will need it...

Update: 1980 CV Electrical Issue

banjoman09

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RogerinIowa

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Donaldinky

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gab

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banjoman09

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