The Stovebolt Site Forums The Shop Area The Electrical Bay Prepping for wiring harness replacement...

I have been having some electrical issues in my 58 Suburban. The original 235 has been swapped for a 250 at some point. Whoever did the swap must have grabbed half the wiring harness from the donor vehicle. I had a bunch of wires hanging down and wires that weren't connected to anything when I got it. After a lot of quality time with a multimeter tracing wire and checking continuity I had a decent size pile of scrap wire on the garage floor.

That was 10 years ago. Since then I have done a fair amount of wiring/changes. When I was too ignorant to know better I just used whatever wire was the right gage and was cheapest. Needless to say there is a lot of red wire under the dash. This and some electrical gremlins have lead me to the conclusion that I need to replace the wiring harness. That is a separate thread for the electrical bay forum.

My question here is what should I do to prepare to replace the harness. I'm thinking remove the seat, pedals and gage cluster. I'm also considering removing the steering column. Does the whole dash remove "easily?" Is that worth the trouble. Put the truck up on jack stands and take the wheels off to make undercarriage wiring easier? Remove the hood? I'd like to neatly run the wiring in accordance with the assembly manual so access to tight spaces is important.

I'd rather take the time to make the job easier so I can avoid dislocating a limb or swearing a blue streak.

Thanks

Larry

Larry, Since your question is focused on your wiring harness repairs on your 'Burb, I've moved the conversation over to the Electrical Bay where it is most likely to get the best answers and helpful input. Others will be along soon to offer help.

I am prepping to do the same thing. I am doing a truck, so it will be somewhat different than your suburban.

I pulled the gauges, but not the column or the seat because the column is pretty easy to work around and none of the wiring runs under the seat, inside the cab. The dash itself is spot welded in.

My harness has:
1. fuse block
2. A bundle of wires the run into the dash for the gauges/radio/hvac
3. A bundle of wires for the engine
4. A bundle of wires for the front (lights, horn, etc)
5. A bundle of wires for the rear (fuel sender, lights)

Each of those bundles (except the dash harness) goes through a grommet in the firewall, then is routed outside the cab to the correct locations.

I intend to lift the truck to run the bundle to the back, but leave it on the ground and work from the top for the rest.

Fibonachu:

Thanks for the advice.

I was only removing the seat and column to make more room/easier access. Like I said, I'm tired of having to lay upside down and sideways and dislocate my shoulder in order to reach up behind the gage cluster. Thought it would be easier with an open spot to lay down and no column in the way. The seat should be easy. I have no idea how hard it is to take the column out. Sounds like the dash isn't coming out. 🤔

I'd like to replicate the factory wiring routing and want it to be neat and properly organized. I have a bad habit of making it good enough in order to get back on the road instead of doing the job right. I don't want to half-do the wiring. I imagine when they ran the wiring at the factory there wasn't much in the cab to get in the way.

Like I daid, the dash is spot welded in place. Getting it out is a big deal.

If the steering column is original, the correct way to remove it involves either lifting the body off or disassembling the whole steering system because the column shaft is pressed into the steering box and they come out as a monolithic unit.

The dash wiring is pretty minimal. You can do all of the gauge/switches work on the floor in the driver footwell and reach through the gauge hole to route it. After that, there are only like 3 wires going across the inner firewall (assuming a stock setup) for the radio and heater blower motor.

It would be a judgement call whether it is worth the effort to pull the seat.

The other thing that you might consider is the condition of your bulb housings/sockets. I pulled my bulbs (headlights, parking lights, etc) and cleaned, repaired, prepped all of their mounts ahead of time so that once I get the new wiring in, I can reassemble those parts and be done with them. I didn't want to get distractes halfway through the wiring by needing to replace a headlight adjustor.

My goodness. Its uncomfortable for certain. Most go to the cluster
which you can pull partially out to wire. The IGN can be done thru that opening.
The light switch same thing. wiper and heater are difficult.
Put a pillow down where you need it. Light the under dash up good.
Start to hurt...stop.


Removing the column and/or seat is way too much work.

Hooah! Sounds like the column isn't coming out either. 🤦‍♂️

I like the tip about servicing the light sockets ahead of time. That should save some headaches and delays.

One last question. Can you recommend a basic load of spares or special tools to have on hand? I plan on the basics (solder, soldering iron, heat gun, heat shrink tubing, multimeter, zip ties etc.) Any tricks of the trade tools or gadgets I should have?

I'd add some split or spiral wiring loom tubing. Spiral is harder to put in place, but sturdier.

I used some vinyl harness wrap I got from Summit Racing when I repaired/modified my harness. It's non-adhesive and very similar to what was used originally. It wraps on very nicely (is a bit stretchy), but takes 2 people to wrap the harness. The starting point is easy enough to secure by sticking it between the wires in the bundle, and the same method at the ending point with a little electrical tape for extra security. I wrapped the whole harness in one length of wrap, with my daughter providing the second set of hands. It took us less than 30 minutes.

Excellent ideas. Thanks!!