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Topic: WIndow Weirdness

in Forum: C3 Electrical


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WIndow Weirdness (1/15)
 8/10/23 12:00pm
w4xtc
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Lucama, NC - USA

Vette(s):
1979 L48


Joined: 1/22/2010
Posts: 5

The car is a '79 with power windows. Driver's side window would not go down. Pressing the switch in either direction caused the voltmeter to dip, indicating current draw. I checked the connector at the motor, and had 12 volts, up & down. Suspecting the motor (it was the original), I pulled it and bench tested it. It worked, so I gave the gear a good cleaning, re-lubed it and re-installed. I went ahead and cleaned the connector contacts and applied dielectric grease while I was in there. Voila! Worked fine. Buttoned everything back up. Still worked. Next day... window would not go down, same symptoms as before. I replaced the motor with a brand new one. It worked perfectly. Ran it up and down several times. A couple of days later I drove the car with the window down and parked it in the driveway. After dinner, I went outside to put up the windows and, you guessed it... the driver's window would not budge. Again, the volt meter dipped when I Pressed the switch. Determined to not pull the door panel off again, I closed the door, started the car and after moving the switch a few times, the window went up. I cycled it up and down a few times and it worked fine. Any ideas as to why this window is so hit or miss? Maybe it's the regulator and not an electrical problem? Looking for input.

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Re: WIndow Weirdness (2/15)
 8/10/23 2:34pm
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.


Joined: 7/9/2003
Posts: 862

When I installed my factory power windows about 40 years ago, I seem to remember there being a relay involved. I don't remember exactly where it was located but I suspect it was under the console with the switches.

I'll try to look in the factory service manual when I get back. 



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1973 L-82 4 spd

Re: WIndow Weirdness (3/15)
 8/10/23 9:48pm
Adams' AppleLifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


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1979 would not have a relay. The power windows run from a circuit breaker in the fusebox. Could be a faulty circuit breaker, or wiring issue. 



|UPDATED|8/10/2023 7:48:13 PM (AZT)|/UPDATED|


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Re: WIndow Weirdness (4/15)
 8/11/23 12:00am
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.


Joined: 7/9/2003
Posts: 862

If it doesn't have a relay, that would mean all the motor current would pass through the switch. In that case I would definitely check the switch or replace it. 



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1973 L-82 4 spd

Re: WIndow Weirdness (5/15)
 8/11/23 10:05am
w4xtc
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Lucama, NC - USA

Vette(s):
1979 L48


Joined: 1/22/2010
Posts: 5

Indeed, '79's do not have power window relays. The entire load is carried through the switches. I'm reasonably sure the breaker/power source is not the culprit, as both left and right switches are fed from the same breaker and the passenger-side window works normally. I got a current draw when I pressed the switch in either direction, which led me to believe the switch was working. The only load on the circuit is the motor, and since the voltmeter is dipping when I press the switch, I figured the switch must be sending juice to the motor. Ditto, why I ruled out the wiring to the door. I suppose the switch could be worn to the point where its' internal resistance is above normal? At the moment, it works. It's probably waiting for a downpour to decide it doesn't want to go up, lol.  

Re: WIndow Weirdness (6/15)
 8/11/23 4:04pm
Adams' AppleLifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


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Swap the connectors on the switches. If the ds window works but the ps stop working, then you know the switch has failed. Switches are in the console, correct? 



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Re: WIndow Weirdness (7/15)
 8/11/23 4:39pm
w4xtc
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Lucama, NC - USA

Vette(s):
1979 L48


Joined: 1/22/2010
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Yep, switches in the console. Good suggestion! 

Re: WIndow Weirdness (8/15)
 8/11/23 7:49pm
manchestersharkLifetime Member
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Equinunk, PA - USA

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Them buggers are noted for that. Don't get new ones from R.O.C. auto. Find O.E.M. ones. They'll last till your done with the car. 



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Re: WIndow Weirdness (9/15)
 8/12/23 12:10am
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.


Joined: 7/9/2003
Posts: 862

If it turns out the switch is bad, I suspect it's due to contact resistance that's built up over the years.  The reason you got a current draw was because even with high resistance, there could be a minor amount of current draw but not enough to run the motor. 



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1973 L-82 4 spd

Re: WIndow Weirdness (10/15)
 8/14/23 8:26am
w4xtc
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Lucama, NC - USA

Vette(s):
1979 L48


Joined: 1/22/2010
Posts: 5

Thanks, everyone. Good suggestions. I have a new switch on the way, but will first try to disassemble the old one and clean the contacts. Most likely the OEM switch is of better quality than the new reproduction.

Re: WIndow Weirdness (11/15)
 8/15/23 3:21pm
kstyerLifetime Member
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CUYAHOGA FALLS, OH - USA

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The C3 window wiring is different than anything today.  In newer cars the switch operates a relay.  In ours no relay.  Instead the switches switch a hot lead between up power and down power.  They go to the window motor.  Instead of reversing polarity, they have a seperate ground in the door.  The key here when the door is open it won't work.  When the door is closed the it makes a ground connection.  You lost the ground in the door from the motor to the chassie.   To confirm connect a ground wire from the motor to a good ground  with the door open and operate the window.

When the window goes up it requires more power than going down.  The ground has not Totally failed, but is going bad. 

Re: WIndow Weirdness (12/15)
 8/16/23 5:38pm
Reds82CELifetime Member
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McKinney, TX - USA

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1982 Collector Edition, Silver-Beige metallic, 40000 miles and counting. 2015 Z51 Red Convertible


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kstyer, you got me thinking about my driver window refusing to go up all the way unless the door is open.  I have messed with the alignment and think its as good as it will be.  So, its possible the motor is too weak after 40 years.  Does anyone know what the ohm's reading is that a good motor should draw?  Do these motors have a power cut off capacitor when the window is fully up to prevent the motor burning out?



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Re: WIndow Weirdness (13/15)
 8/16/23 6:41pm
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.


Joined: 7/9/2003
Posts: 862

A possible reason that the window does not completely go up with the door shut is the assist spring is getting weak. As soon as the window contacts the weather stripping, it requires a little more force to overcome the friction of the weather stripping. 

The purpose of the spring is to balance out the amount of force the motor has to overcome whether it's raising or lowering the window. 



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1973 L-82 4 spd

Re: WIndow Weirdness (14/15)
 8/16/23 7:13pm
Reds82CELifetime Member
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McKinney, TX - USA

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1982 Collector Edition, Silver-Beige metallic, 40000 miles and counting. 2015 Z51 Red Convertible


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I should have mentioned that I rebuild the window with new regulator and rollers.  The regulator x-joint was very loose.  the only window part I did not replace was the motor.  the car only has 45,000 miles and the passenger window works great and still has the original parts.  I also took the motor apart and cleaned all the internals, magnets were good, re-greased, ect. I didn't replace the motor due to cost and it was easy to clean, but would if there was a way to measure the motor under upward stress to know if it is weak.



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Re: WIndow Weirdness (15/15)
 8/16/23 7:19pm
73shark
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Overland Park, KS - USA

Vette(s):
1973 Orange Metallic Coupe (orig owner), L82, 4 spd (WR), PS, (A/C & PW (I installed from wrecked 73)), leather, AM/FM Stereo, ran with '65 FI unit earlier & will again some day.


Joined: 7/9/2003
Posts: 862

You could try pressing downward on the window with the door closed and attempt to raise it to see if it made a difference in the position of the window when the motor quit.

You could also try doing the same thing on the passenger window to see if that side has more strength. 



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1973 L-82 4 spd

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