Power window issue

oberger

Regular user
Hi all, I'm having some issues with my power window. When I bought the car they weren't connected. First of all I tested the motors with 12V directly and they work perfect, however they are Bosch FRE 12V and not the original ones. After reading a lot from Willcoxon and corvette forum, I follow all the instructions to follow the electrical scheme and test the circuit breaker, relay, and switches with a 12v light screw and everything seems to work, or at least turn the light. Nonetheless I have power from the switches to the motor, they are no able to function from the circuit power.
Any idea about what this can be? good motor, apparently good electrical circuit but not working together?
I want to try to fix myself the problem, because this is where I found the fun! but if I'm not able, any electrician in norther London?

Thank you!
 

Daytona Vette

Well-known user
So the switch works and the motor works, but the switch feed is not powering the motor - look for a brake in the wire at the hinge point of the door, the switches can be temperamental, (I have junked a couple of new ones) check the earth to the motor is good - best of Luck!

PS let us know how you get on
 

oberger

Regular user
Thank you for your quick reply. Hope this weekend I can find the solution. How to check the earth to the motor?
Regards,
 

johng

CCCUK Member
I had a similar issue with mine. I had continuity through the switch, but it wouldn't pass enough current to operate the motor. I took the switch apart, cleaned up the contacts, put it back together and it all worked. Might work for you.
 

oberger

Regular user
Take a wire direct from the battery to the earth terminal on the motor to see if that gets it working
Dear Daytona, it wors! I grounded the motor direct from the battery and connected one of the wires from the switch and the motor workes! So the issue seems to be ground to the motor.
According to the wiring diagram below, I only see ground in the circuit in the relay and I think that ground it's working because the relay seems to work fine. (I assume). Do you think it goes something to be with the old wires? both conducted the 22 V to the motor.
My multimeter reading was: battery 18V, Relay 21V, Switches 22V, wire at motor 22V Is it normal? more than the car battery?

Thank you so much again for all your help!PW_wiring_76.JPG
 

Custom exotics

Well-known user
The motors are grounded though there casings the 2 wires to the motor are both live feds to drive motor up or down you might have issie that door itself is not ground to main body of car through the hinges you could run a new earthwire through the door gromet
 

oberger

Regular user
The motors are grounded though there casings the 2 wires to the motor are both live feds to drive motor up or down you might have issie that door itself is not ground to main body of car through the hinges you could run a new earthwire through the door gromet
I Tried ground from the door and motor case and connecting there the light pen and touching the + of the battery there is power, so I think there is ground in the door and motor. I think the motor cables with one position of the switch one must be + and the other - (ground) so I´m think the problem is with the ground through the cables..... any suggestion?
 

teamzr1

Supporting vendor
You need to make clear if you mean BOTH power windows do not work, work one direction or just 1 window and which

What is the junction block connection tied to ?
Answer would change knowing answers at top ?
Are you sure the relay is working correctly and proper ground to it ?
I would check splice #70
I would think case of motor goes to chassis ground

Suspect relay or its wiring but need more info
 

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oberger

Regular user
You need to make clear if you mean BOTH power windows do not work, work one direction or just 1 window and which

What is the junction block connection tied to ?
Answer would change knowing answers at top ?
Are you sure the relay is working correctly and proper ground to it ?
I would check splice #70
I would think case of motor goes to chassis ground

Suspect relay or its wiring but need more info
Dear Teamzr1, both power windows do not work in any direction. If I connect a cable from the battery (-) to one of the motor pins and one of the cables from the switch the other motor pin, works fine in one direction!, then change the cables and the motor works in the other direction. Same in both doors.
Not 100% sure if the relay works fine, at least I read power from the relays connections and it´s grounded itself to the body of my car.

What is the junction block connection tied to? I´m sorry I don´t understand that....I think connection 70 wors because both switches have power.

Thank you for your help!
 

johng

CCCUK Member
I think your problem is that you don't have the correct motors. As far as I am aware the C3 motors need +12v on one of the 2 pins (one pin makes the window go up the other pin makes the window go down) and the earth goes through the case. The motors you have seem to require +12v on one pin and earth on the other. The current wiring does not supply that, so you either need to completely re-wire the motors or get the correct ones.
 

oberger

Regular user
I think your problem is that you don't have the correct motors. As far as I am aware the C3 motors need +12v on one of the 2 pins (one pin makes the window go up the other pin makes the window go down) and the earth goes through the case. The motors you have seem to require +12v on one pin and earth on the other. The current wiring does not supply that, so you either need to completely re-wire the motors or get the correct ones.
Are you sure? according to the wiring diagram earth it's only from the relay but I can´t imagine how can travel (-) through a wire and (+) through the other and then switch from + to - and - to + to the motor pins.
 

teamzr1

Supporting vendor
Yes sounds correct JohnG
The motors needed have B+ 2 wires, each go to 12 volts coming from each side of window switch and motor gets ground from motor
case to chassis ground

There is 2 voltage sources
1 is from Ign switch so when key on supplies 12V to coil of relay
other voltage goes to 30 Amp fuse to input side of relay and what the motors use

3rd pin of relay then supplies output voltage to wire (slice 70) that then supplies voltage to center pin of each window switch
the switches then depending on which direction the button is hit then supplies voltage to either up or down position

So the correct window motor needs to be designed so voltage to either wire makes motor go forward or backward (UP/Down)
If the motors you have expect 1 wire B+ and other ground then wrong motor
For any testing the motor needs a ground source to work.

If suspect the relay, unplug it and then use a Jumper wire and jumper from the input (from breaker) (orange/black)
to (red/white wire) pin and see then if voltage to red/white of window buttons.
Check for voltage then to each other pins of button switch depending which side of button is pushed

As to the 2 wires going to motor then you should also see 12V to each as button direction pushed

If not certain about motor design, take motor off chassis ground, no wiring connected from switches
and using Ohm meter, one side to motor case and other to each 2 wires of motor should be high impedance ( little resistance via relay coil )
If Ohm meter shows a direct ) ohms then 1 motor wire is a ground and wrong design for your C3.

At the least if motor is to chassis ground and motor wires not connected then touch one wire from button to 1 motor wire and see what happens or touch instead to other motor wire and see if mother then turns

Do not know if there is not some type of limit switch involved.
 

teamzr1

Supporting vendor
Are you sure? according to the wiring diagram earth it's only from the relay but I can´t imagine how can travel (-) through a wire and (+) through the other and then switch from + to - and - to + to the motor pins.
Read what I just posted.

Easy Ohm test to see if the motors you have are designed as 1 positive and 1 negative (ground) or
proper design is each wire causes different direction of motor arm
Simple, look at the window buttons, all you see is 12 volts from relay center pin and then depending on which button makes contact is then supplying the same voltage to either motor wire.
NO ground switching, only ground is motor case to chassis ground
 

johng

CCCUK Member
I'm pretty sure that your problem is that the motors you have aren't compatible with the wiring in your car. The easy (but expensive) fix is to get a pair of the correct motors. You could re-do the wiring in your car, but I think you would need 2 pole switches that can handle the current drawn by the motors and that would fit somewhere in the car. It might be possible to use some relays, but you need a better electrician than me to work that out.:)
John
 

teamzr1

Supporting vendor
If motor was designed to change rotation by which of the 2 wires get B+ (12V) then I would check wiring and type of relay

Coil of relay needs ground and 12V. As mentioned the wire from Ign switch supplies that voltage to one side of coil and other side ground
With ign key off measuring with multi meter, one side ground

1. Only voltage from 30 amp fuse to correct pin to relay, check, pull 30 amp fuse, now no voltage to any pin of relay
2. turn ign key on while fuse still pulled and now only voltage is read to coil
3. is it the correct type of relay ?
with ign switch off, the contacts should be normally open
4 with ign switch on (and fuse back in) then there should be voltage to pin that goes to wire that supplies voltage to center pins of both window switches
 

oberger

Regular user
Dear John and Team ZR-1, now I know that the motors are the cause of my problem. I connected ground (-) terminal from the battery to the motor case and + to any of the pins and the motor doesn't run. So my Bosch motors are designed to have + and - to the pins in an alternative way. why they are in my car? have they worked before there? don´t know because the car was with power window disconnected when I bought it. What can I do now? original motors are expensive, probably the same price as an electrician to solve my problem.

Thank you very much for your help, now I know the reason why power windows don't work.
 

teamzr1

Supporting vendor
Hi Oberger

I suspect last owner tried fixing power windows and bought wrong ones and could not figure out how to fix the problem

If they only looked at that wiring drawing it would be clear the window button was switching 12V to either wire of
motor to switch up or down direction :-(

Can you do Amazon in your country, and is $47 each too much money for where you are at ? (say free shipping, not sure also for UK ?)
They have both left and right sides and is cheaper like $25 then Rock Auto sells them

https://www.amazon.com/Evan-Fischer...---------&vehicleName=1976+Chevrolet+Corvette

Shows longer warranty can be bought
Add a Protection Plan:

3-Year EXT - Automotive Parts ($25-50) for $12.05

2-Year EXT - Automotive Parts ($25-50) for $9.40

This help you ?
 

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Custom exotics

Well-known user
You def have wrong motors the motors you have require a reverse pole to make the them go opersite way eg +to + -to- to go up +to- and -to+ to go up only way to do this is via 2x 5pin relays to each side of car
 
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