Wiring -- rip out and start fresh?

[maloryII]

My 72 needs to be completely rewired. I have no experience wiring stuff, but I'd think to think I have half a brain and can follow wiring diagrams.

What do you guys think, is it better to just tear everything out and start from scratch? Or troubleshoot wire by wire until everything is as it should be?

[Boog]

I would think it is a matter of just what condition your original harness is in. What kind of problems do you have going on with it?
Start by going to the battery and making darn sure you have good clean connections at the battery before trying to diagnose electrical probs. Then check all other ground wires and remove and clean each one as good insurance. They may look ok and still be corroded underneath.
If you have never done any electrical work replacing an entire harness is still doable for a beginner. There's not as much to it as you might think on these old trucks.

[jaros44sr]

Originally Posted by maloryII

My 72 needs to be completely rewired. I have no experience wiring stuff, but I'd think to think I have half a brain and can follow wiring diagrams.

What do you guys think, is it better to just tear everything out and start from scratch? Or troubleshoot wire by wire until everything is as it should be?

I just went with a M&H wiring harness, they can modify it to anything you want, but so far it has been plug and play. No brain required, only plugs in one way

My mods were
Key switched electric choke
Relays, Hi and Low beam
SI internal voltage regulater, passenger side
HEI hook up
Tach hook up
Both of the above just plugged into the HEI

[maloryII]

Originally Posted by Boog

I would think it is a matter of just what condition your original harness is in. What kind of problems do you have going on with it?
Start by going to the battery and making darn sure you have good clean connections at the battery before trying to diagnose electrical probs. Then check all other ground wires and remove and clean each one as good insurance. They may look ok and still be corroded underneath.
If you have never done any electrical work replacing an entire harness is still doable for a beginner. There's not as much to it as you might think on these old trucks.

It's more of an issue of almost nothing is correctly hooked up, or hooked up at all.

The wiring harness is pretty rough. Everything is totally "redneck engineered" and just needs a good going through. The headlights, tailights, and brake lights work, amazingly. But there are dozens of wires that aren't attached to anything.

[Skirkpat]

Looks Perty, I always used M&H on my Chevelles, costs alot, but very nice stuff!!!!

[Skirkpat]

Originally Posted by maloryII

It's more of an issue of almost nothing is correctly hooked up, or hooked up at all.

The wiring harness is pretty rough. Everything is totally "redneck engineered" and just needs a good going through. The headlights, tailights, and brake lights work, amazingly. But there are dozens of wires that aren't attached to anything.

I would find a nice donor truck, old/shabby wiring is not good, I would spend my cash on wiring right after BRAKES and SUSPENSION.

[vectorit]

If you have the dough, then I'm sure M&H wiring would be happy to hear from you!
Seriously, if the wiring right now is all hacked up then it wouldn't hurt at all to replace it. You don't even have to replace the whole thing, you can replace the engine harness or tail light harness. That unless you go with OEM style for the year of your truck.
If anything you will rest a little easier knowing that your truck won't have an electrical fire some day, just because the PO did something creative to the wiring.
As far as skill is concerned, I am electricity challenged for sure, but the harnesses are all keyed in a way that let's you plug things in one way.
Get a test light too, they only cost a couple bucks and they help with simple diagnostics.

[maloryII]

Thanks for the posts guys.

I assume the wiring harness is the central box located under the driver's side dash where all the stuff plugs into? The one with the fuses?

With that replaced, I just trace all the wires to their respective locations and ensure they're plugged in correctly to the harness?

Sorry for the dumb question.

A test light sounds like something I need.

[Skirkpat]

The main wiring harness is under your dash, and includes the fuse box, thn there are two harnesss under your hood that plug into the main on the firewall, on is for front lights one is for engine. If you have unplugged or spliced wires it is a good idea to figure out what they are and where the go. Wiring is pretty simple you have positive and negative, they should never touch.....or you will have whats called a short (sparks are real bad).

Buy a test light for a couple bucks and remember that the whole truck (metal that is) is a ground (-) that is why your battery connects to the frame, everything on it will act as a ground (-).

[maloryII]

Originally Posted by Skirkpat

The main wiring harness is under your dash, and includes the fuse box, thn there are two harnesss under your hood that plug into the main on the firewall, on is for front lights one is for engine. If you have unplugged or spliced wires it is a good idea to figure out what they are and where the go. Wiring is pretty simple you have positive and negative, they should never touch.....or you will have whats called a short (sparks are real bad).

Buy a test light for a couple bucks and remember that the whole truck (metal that is) is a ground (-) that is why your battery connects to the frame, everything on it will act as a ground (-).

Will be looking into it. Thanks!

[jaros44sr]

That harness is already 40 years old, add the fact that it has been cobbled. Even if you find a used harness, there are wires that have melted in the past, but you can't see them unless you untape it. Soooo, the next time that wire gets a little hot, could be the one time it melts thru the insulation and sets your project on fire.

Not worth the risk in my book...all the hours and money up in smoke. I'll spend the money now

[big_al_71]

What we did on my truck was exactly that just ripped out all the wiring then I ordered brand new harnesses. One of my guys rewired my complete truck including extending all the wires in the engine compartment as you cant see not one wire in my engine compartment took him about four days working on it about 5-8 hours per day. I could not be happier.

[Musclerodz]

American Autowire now has their Classic Update kits available. It covers the entire truck for $539 retail. It includes 95% of everything you need to install. minus door jamb switches and A?C harness if you have facotry a/c. M&H factory stuff and AAW factory fit will cost nearly twice that for every harness to rewire the truck. I have the classic update kit on sale for $485 right now with free shipping for another week. We have a thread on them in the for sale section.

[cdowns]

lots of harnesses are replaced for no need

first thing to do is to get the stock wiring diagram
then the wires you find disconnected ID them are they part of the original harness or addons??
if they're not original i always isolate and remove them one wire at a time until all that is left is the original wiring . then i go to work inspecting each individual wire either repairing or replacing each wire one at a time

do all this work with battery disconnected

[cparman]

ditto to all of the above. Why in the heck would you want to be a chasin a wiring problem after all of your hard work? I bought EVERY harness for my 67 Chevelle from M&H. it was a plug and play, and NEVER had a problem. It is the way to go. Pricey but well worth it!

[Bpokey]

The wiring in my 68 was so hacked up I had to replace it all. I went with an EZ wiring universal 21 circuit. Probably not as easy as Painless or some of the more expensive kits but if you don't mind using a little ingenuity it is a heck of a lot cheaper. Got mine on Ebay for $160.

[maloryII]

Thanks for the posts guys, given me a lot to think about!

I think I'll take everything out except the ignition (which is jury-rigged to a toggle switch) -- as long as my wife thinks our truck is "running" it doesn't make me look as bad!

[Hammer57]

Repro harnesses are okay IF you're going back full stock. A little hint, got a full 20 circuit bumper to bumper set off a vendor at the Auto Fair event here at LMS with mini fuse block & separate flasher relay block. Half the price of a 18 circuit Painless kit and the GM connectors are INCLUDED!
From an outfit called It's A Snap.