When to install your wire harness?

[gottwake]

So im painting the body panels separately and was planning on assembling the truck as they are finished.

Should I install the wire harness before complete assembly or after?

Of course marker and tail lights would have to be connected later if I choose to do it before assembly.
Just looking for what might be best route to take.

[LockDoc]

Originally Posted by gottwake

So im painting the body panels separately and was planning on assembling the truck as they are finished.

Should I install the wire harness before complete assembly or after?

Of course marker and tail lights would have to be connected later if I choose to do it before assembly.
Just looking for what might be best route to take.

Nice truck!

I usually install the dash pad before the under dash wire loom, or anything else in or around the dash for that matter. Otherwise the mounting nuts can be a bear to get to. Other than that it really doesn't make much difference. I also try to remember to install the headlight harness before I put the hood on because it makes it easier to run the loom between the fender and inner panel on the drivers side....

LockDoc

[LS short box]

As said above Dash pad first.
Mine is a LS swap so layout engine harness (same for sbc or bbc) with the painted cab on. No doors or front sheet metal/box on yet. I ran the front harness down the inside left frame rail to the rad support. Same with the rear harness. It was a Painless harness so the wires were plenty long.
Lot's rubber lined wire clamps to keep everything secure. I hate wiring so I take it slow.
Couple of pics.

[MikeB]

It's a lot easier running wires to the rear with the bed and fenders off. Also, leave the seat and carpet out, along with the instrument panel. It's much easier to get to all the dash wires that way. Also, install the fuse panel before you install the front fenders. Again, it's easier access.

[Accelo]

I am not sure about the Painless harness but the American Auto Wire harness requires enlarging the hole, for the large connector, in the firewall. I would cut that in, before painting, if required. I also recommend making the grounds before painting. The back of the tail lights is one place the assembly grounds, if you don't have a narrow box . Also a small hole in each rear inside panel for the ground on the marker lamps. Much easier to mask grounds off first.

[sick472]

I've always started the wiring harness' before the front clip goes on and the interior goes in. From the cab back is not difficult if assembled, but easier if not.

Obviously, some of the wires will not have a place to fasten too until the front clip is on. Those can be bread-tied out of the way until later. My though is that is easier for me to fight the fire wall wiring by standing on the ground to the side rather than on a step stool.

Nice color combo!

[kev2809]

havent done any paint on mine yet but i did my harness with the truck somewhat together. like what others say, please do the dash harness before the pad! those 2 corner screws are so hard to get to. i also have an ls motor so i wanted to have my front clip on so i could route the wires in case the stock routing wouldnt work.

also, that truck is going to look nice!

[68 C10 Driver]

I painted there interior of the truck, and started installing the interior harness. I will paint the firewall and start connecting some of the firewall pass-through wiring.

[MikeB]

Originally Posted by Accelo

I am not sure about the Painless harness but the American Auto Wire harness requires enlarging the hole, for the large connector, in the firewall. I would cut that in, before painting, if required.

Good catch. At least that's the case with the 67-72 "Classic Update" kit, because they are made to fit square bodies. However, on a 66 in did, the fuse panel fit right into the existing cutout. Go figure.

[gottwake]

Originally Posted by LockDoc

Nice truck!

I usually install the dash pad before the under dash wire loom, or anything else in or around the dash for that matter. Otherwise the mounting nuts can be a bear to get to. Other than that it really doesn't make much difference. I also try to remember to install the headlight harness before I put the hood on because it makes it easier to run the loom between the fender and inner panel on the drivers side....

LockDoc

I see you guys mentioning wiring before a dash pad, but what if you dont have one? Does that pose any issues?

[gottwake]

Originally Posted by kev2809

havent done any paint on mine yet but i did my harness with the truck somewhat together. like what others say, please do the dash harness before the pad! those 2 corner screws are so hard to get to. i also have an ls motor so i wanted to have my front clip on so i could route the wires in case the stock routing wouldnt work.

also, that truck is going to look nice!

Thanks Kev....ive been working on two trucks at one time.. so its a waaay slower process.

[LS short box]

I did my Painless fuse box a bit different than most. I filled the stock fuse block hole. Then I took the Painless fuse box and moved it back away from fire wall about 1 1/2 inches attaching it to side panel near the lower vent with "L" brackets. Then I made a small hole in the firewall for the front harness wires. I used a grommet from something to seal up the fire wall and protect the wires. You don't need a big hole as there aren't many front harness wires.

[gottwake]

Originally Posted by LS short box

I did my Painless fuse box a bit different than most. I filled the stock fuse block hole. Then I took the Painless fuse box and moved it back away from fire wall about 1 1/2 inches attaching it to side panel near the lower vent with "L" brackets. Then I made a small hole in the firewall for the front harness wires. I used a grommet from something to seal up the fire wall and protect the wires. You don't need a big hole as there aren't many front harness wires.

Do you have pics?

[MikeB]

Photos below are from an 82 C10 I wired using a universal AAW kit. The black filler plate is an electrical outlet cover with engine compartment and lighting wires running through a grommet. I eventually painted it body color.

I mounted the fuse panel using a standoff because there are so many wires coming out the back.

I used 8ga wire to feed the stud, and then 10ga wires to the ignition switch and fuse panel BATTERY bus. That resulted in essentially zero voltage drop to switch and panel, and only a few tenths to high beams and brake lamps.

[LS short box]

Sorry I don't have pics of the under dash fuse block mounting. I ran the heavy gauge wire for the fuse block from the starter stud to the Painless Maxi fuse and then into the cab thru the same hole I made for the engine ECM harness. You can see the the Maxi fuse just below the heater housing.
I mounted the battery in front of the right rear tire.