77 C30 Power window & Lock wiring issues

[91frppgt]

Hey guys, new to the forum here.

I'm currently wiring a 77 C30 dually. Restored it, and swapped a gen5 6.2 in it with 8l60. I've got everything squared away but the power windows and locks. I did put the relays in the windows. I think I have a grounding issue going on, but not sure what that would be. The wires are hooked up correctly per the instructions. The windows function and go up and down fairly decent as wired to the instructions. If I unhook the ground from the relay, they go real slow much like the factory setup, so i've had the ground off while testing.

What i've noticed is the windows travel up real quickly and get 12v at the switch going up. It appears to work as intended. But going down, the windows get 6-7v and you can tell they are struggling.

The truck is charging correctly, and battery is a new interstate that is holding up. I acquired this truck without any wiring, i'm using a american autowire harness. I have the factory harness in the doors that I am currently using.

For the power locks, can I use a relay like for the power windows? The switches I have for the power lock doesn't fit the electrical connection. Do I have the wrong switch? I'm not seeing how the switch will plug into the electrical connection. The power locks have 3 wires. 1 appears to be constant power, the others are 12v for lock and unlock correct? I do know there is a relay in the factory trucks, but I'm fairly certain I don't have one in the truck.

Thanks for any help you can provide. Pics for attention.

 

[Snoots]

That's the right switch but that connector sure doesn't look right. That appears to be a window connector. I can't tell for sure.
You need to make sure you have a ground strap from the engine block to the frame AND from the frame to the body at the front clip.
Don't try and test it without these grounds. You're wasting your time.

 

[91frppgt]

That's the right switch but that connector sure doesn't look right. That appears to be a window connector. I can't tell for sure.
You need to make sure you have a ground strap from the engine block to the frame AND from the frame to the body at the front clip.
Don't try and test it without these grounds. You're wasting your time.

That's what I was thinking. I'll see if I can find another connector.

Ground is fine on the truck. I have a ground strap from the motor to frame and frame to body at the front clip. All grounds are touching bare metal. This is the only electrical issue i'm having. The rest of the truck is wired. Truck runs and drives. Vintage air works fine, gauges, all lights.

For it to be acting the way it is, I do believe there is a grounding issue. I just need to figure out what is going on.

 

[91frppgt]

Can anyone tell me how the window motor is grounded? On the existing old harness to the windows, there is a black ground with a terminal. I wired it a ground on the steering column, and the ring terminal is wired on the front door channel bolt post. Still have something odd going on. When I ground the relay, the window is super slow.
Looks like I found another issue with the courtesy lights, those don't seem to be getting grounded either. I get 12v on white/orange constantly. I have all my grounds on the dash bolted to one of the bolts that hold the dash in, and its sanded to bare metal.

 

[91frppgt]

FYI both passenger and driver door are doing the same thing. Can rule out the switches.

 

[91frppgt]

I have noticed on the power window switch, I have 5 wires. Pink/brown/blue/bluewhite/lightbrown. I don't see any grounds on the switch itself. I have a new connector but didn't install it. Don't think it will change anything.

 

[Snoots]

Window motors are grounded to the door frame.

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[91frppgt]

thats exactly how I have it hooked up. I have something else going on. Thanks for the response Snoots. Let me do some more digging.

 

[91frppgt]

https://www.gmsquarebody.com/threads/window-switch-color-code.13781/

post #8 states on 77 the black ground on motor frame stud. i'm assuming they are referring to one of the 2 that hold the frame into place? or does it go further down onto the motor itself?

 

[91frppgt]

If I unplug one relay it works as intended I believe. a full 12v and the motor sounds good. Once I plug the other relay back in, it acts funky.

 

[mtbadbob]

Hey guys, new to the forum here.

I'm currently wiring a 77 C30 dually. Restored it, and swapped a gen5 6.2 in it with 8l60. I've got everything squared away but the power windows and locks. I did put the relays in the windows. I think I have a grounding issue going on, but not sure what that would be. The wires are hooked up correctly per the instructions. The windows function and go up and down fairly decent as wired to the instructions. If I unhook the ground from the relay, they go real slow much like the factory setup, so i've had the ground off while testing.

What i've noticed is the windows travel up real quickly and get 12v at the switch going up. It appears to work as intended. But going down, the windows get 6-7v and you can tell they are struggling.

The truck is charging correctly, and battery is a new interstate that is holding up. I acquired this truck without any wiring, i'm using a american autowire harness. I have the factory harness in the doors that I am currently using.

For the power locks, can I use a relay like for the power windows? The switches I have for the power lock doesn't fit the electrical connection. Do I have the wrong switch? I'm not seeing how the switch will plug into the electrical connection. The power locks have 3 wires. 1 appears to be constant power, the others are 12v for lock and unlock correct? I do know there is a relay in the factory trucks, but I'm fairly certain I don't have one in the truck.

Thanks for any help you can provide. Pics for attention.

That's a sweet set-up! Not sure on the 8 speed yet, although I love the 6L80's a whole lot! I'm sure you checked the factory harness going through the door into the cab?? Breakage there is very common, could be a partial broken wire, but I'm sure with the extent of $ & time you're putting into that build, you've probably checked that.

 

[Juggernaut]

Are you still using the original window motor from 77? Looks like this

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[Juggernaut]

The lock switch you're showing is the 82 and up style switch. If you're using new lock actuators, it will work. If you have the old style actuator with the flat spade type connector you won't be able to use that switch. You need the high amp switch that fits the connector you're showing. This is the lock harness from my 77 K20

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[91frppgt]

The lock switch you're showing is the 82 and up style switch. If you're using new lock actuators, it will work. If you have the old style actuator with the flat spade type connector you won't be able to use that switch. You need the high amp switch that fits the connector you're showing. This is the lock harness from my 77 K20

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Yup thats the switch I originally had. The later switch I have has the spades in a 45' angle.

So I had figured out the issue. I HIGHLY RECOMMEND to watch this video if you are installing a LMC harness.

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[91frppgt]

The lock switch you're showing is the 82 and up style switch. If you're using new lock actuators, it will work. If you have the old style actuator with the flat spade type connector you won't be able to use that switch. You need the high amp switch that fits the connector you're showing. This is the lock harness from my 77 K20

You must be registered for see images attach

I'm using the old actuators. I was going to get the later pigtails and wire them in. Or do I need to get the correct switch.

Also, can I just use a 30amp 5pin relay to trigger these locks? I will need 2 of them correct? 1 for lock, and 1 for unlock?

Thanks for all you guy's help. Really appreciate it.