Power Window Relay Mod on Rear Window

[Milblazer]

A thought came to me while looking at the relay mod for the power windows in our square trucks. Could that same mod be applied to a power rear motor? It has an up, down, and off position on the switch just like the side power windows. You could pull 12V right off the junction block and splice the relays in right where the wiring exits into the engine compartment. If you use weather pack connectors the system can be used with or without relays in case you're in the middle of nowhere with a relay that went bad you can just unhook the relays and connect the system back to factory.

 

[Milblazer]

Here's my pic that I made following a picture I found on the net

 

[89Suburban]

 

[bucket]

Hey, that's a swell idea!

 

[Milblazer]

Well I built a harness to splice into the factory wiring and I didnt reverse the wires. From my drawing numbers 85 and 86 need to be swapped to work correctly which is why I guess the fusible link I put on burned up. I'll rebuild the the harness and try again as some as some new connectors get here.

 

[Milblazer]

Replaced the pieces of the harness that got all melty and tried again after swapping pins 85 and 86 in the relay mount. Fusible link burnt up again. Glad I added some quick disconnects this time in case the link burned up again. This time it was only one wire that got hot and melted the relay mount. It was the ground 87A. I'm going to look at the wiring schematics again. Maybe the motors are grounded differently.

 

[Milblazer]

Ok, I think I have this figured out. If you look on the wiring for the door power windows you'll see that each switch has a ground wire that connects to the main power window harness which is grounded to the bus bar under the dash. On the rear power motor the switch is not grounded. The only ground I can see is where the motor bolts to the tailgate which is why sometimes adding a ground from the tailgate to the body can make your tailgate window work again. Soooo what does this mean? By adding a ground anywhere in the rear power window system that isn't directly connected to the motor/tailgate will cause the system to become inoperable. Not knowing a damn thing about relays I'm not sure if they need a ground or not to function but if they do I'm going to have to run one all the way to the tailgate or possibly remove them if they are not required. Does this sound right?

 

[Milblazer]

Maybe my pins are not correct

 

[Milblazer]

I'm doing some reading here on how relays work: http://www.rattlebars.com/avalanche/relay_basics.html

Youtube video on 5 pin relays: http://www.youtube.com/watch?v=vupmb2U-shk

 

[Milblazer]

So this should be how things are wired up

Pin 30 12V source in (junction block)
Pin 85 Ground
Pin 86 12V from the switch (up or down from the window switch)
Pin 87 12V to the window motor (up or down)
Pin 87a Ground

 

[Milblazer]

Well with re-arranging my pins to the above wiring I am able to get the harness installed and properly grounded and hooked up to power without burning up any fusible link! Progress is progress. Ok, so now that nothing is smoking right away I turn the key and still no smoke. I'm 2 for 2! I push the button to make the window go up and the dash lights dim and no window going up...crap. Dimming lights and warm fusible link is making me think power is going through one of the grounds when the switch is pushed. I'm thinking I should get rid of the connection at 87A

 

[Milblazer]

Got rid of the ground at 87a on both relays and everything works perfectly. I can say the window does go up and down faster but not by much. I'm talking only fractions of a second faster. I am using junk yard parts too so maybe the motor is all worn out. I'll have to see if a newer motor performs the same.

 

[bucket]

Ah yes, forgot about that. The motor is self grounded and then one terminal is up and the other is down.

 

[jamba]

Thanks

I was struggling with my K5 rear window, searched internet, found this.
Thanks a lot guys!
Seems like a lot of chevy knowhow here

 

[gmachinz]

I've built a few harnesses for the rear gate glass motors-you HAVE to run big heavy gauge wiring to the back as well as a stout ground to body and motor housing. Mounting the relays in the rear is ideal and recently I've added auto down to my rear gate glass harnesses-no more holding the damn switch lol.