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Electrical geniuses needed!!!!

Jake_C_

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Alright I’m dealing with a few electrical issues, as you can see. 76BCF63C-71A1-4A63-9C28-9CBB6D7E04A0.jpeg There are like 3 main circuits I’m trying to get working right. Horn, windshield wipers/washer, and headlights/blinkers. I want to open a thread to hopefully get a few people on here that can help me out. The first question I have is regarding the horn circuit. Specifically the ground. So there’s an orange power wire that goes from the junction block (behind the horn fuse) to the horn relay, that gives power to the relay. There’s a green wire that goes all the way from the second terminal on the relay out to the horn. And there’s a third black wire that grounds and triggers the relay to send power to the green wire. The horn is grounded on the core support. So the ground wire goes from the 3rd terminal on the relay, straight to the steering column connector for the turn signal switch. There’s a little button in that switch that when depressed, will close the ground circuit. But I don’t know how that button is actually getting grounded. Is the steering column grounded just by being bolted in? Or is there a ground feed to the steering column somewhere? Hopefully that made sense.
 

Jake_C_

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What year is the chassis? Wiring diagrams are your friend
88, I’ve been looking through diagrams like crazy but I can’t seem to find everything I need.
 

Bent77

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I have what you want. Not sure where it is at since I just moved

what you’re looking for is “chassis wiring” (as opposed to the engine diagram)
 

Joel Wilson

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I only have up to 87 wiring diagrams, but I do have 88 service manual but its a big file. 67mb so kinda out of email range.
 

Jake_C_

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I only have up to 87 wiring diagrams, but I do have 88 service manual but its a big file. 67mb so kinda out of email range.
I think the 87 diagram would be the same but I’m not totally sure.
 

Joel Wilson

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I only have up to 87 wiring diagrams, but I do have 88 service manual but its a big file. 67mb so kinda out of email range.
I stand corrected. I do have the 88 wiring diagram manual but it's 19mb.

I am sure I downloaded it online somewhere.
 

Joel Wilson

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Here is page that has up to 87.

 

Joel Wilson

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Here is some stuff for 88 and up.

 

TJ1978

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Absolutely. Any pages that cover the headlight switch, turn signal switch, and wipers would be very helpful.
Ok, got it from dad along with some earlier manuals. I will try and find what you're after and snap some pics tomorrow.
 

Jake_C_

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Thanks guys, I’m looking through the diagrams now, should help a ton. I have the horn mostly figured out for now although I don’t have power to the relay from the fuse box right now. I’m not totally sure how the box is fed. I assume different sections get power from different sources, but I don’t really understand that part I guess, do all these wires above the fuses feed the box? Or do they draw from the box and power different systems? 27CD7463-2E22-44B4-8435-2A94C1CF7CC8.jpeg I’m pretty sure the circled area is supposed to be hot at all times and it’s dead right now which is why the relay isn’t getting power I assume. So I need to figure that out and get power back to the box and I should be done with the horn.
 

6872xtc

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Those wires plugged into the fuse panel recieve power for different things. Power comes into the back of the fuse box.

Having those battery hot terminals dead, I would start with checking the junction block on the firewall, inboard of the brake booster, for power. I believe that you can trace one of the wires down to the starter. Check and see if a fusible link is blown at the starter.
 

Blue85

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Alright I’m dealing with a few electrical issues, as you can see..
It seems like the biggest issue is that some yahoo has been tearing your interior out? Do you have monkeys in your shop?

I was just wondering if you did all this teardown chasing these issues or if some/all arose during whatever other project was happening (cluster swap?)
 

Jake_C_

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Those wires plugged into the fuse panel recieve power for different things. Power comes into the back of the fuse box.

Having those battery hot terminals dead, I would start with checking the junction block on the firewall, inboard of the brake booster, for power. I believe that you can trace one of the wires down to the starter. Check and see if a fusible link is blown at the starter.
That’s what I thought but I don’t think the entire box is dead it’s just a couple areas which confuses me. I’ll check that, I re ran part of that wire awhile ago so I’ll have to check the whole thing again.
 

Jake_C_

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It seems like the biggest issue is that some yahoo has been tearing your interior out? Do you have monkeys in your shop?

I was just wondering if you did all this teardown chasing these issues or if some/all arose during whatever other project was happening (cluster swap?)
I tore all of this interior out during this build except the cluster. I took the cluster out to get to all the wiring recently. Although I probably have caused a couple issues, none of these systems worked right when I bought the truck. So yeah the po did a number on the wiring and i probably finished it off over the last couple years of this project.
 

Wes Harden

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So 1987 and 1988 are screwy when it comes manuals.
I remember them being wrong in 88 for gmt400. I would choose the 87 first.
 
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