Technical Question for the wiring gurus

For a 1950 Deluxe. I have a 12 circuit fuse box that was bartered for. I also have a bunch of 12awg stranded THHN wire from a home project. Can anyone tell me if it's ok to use this or why I shouldn't?
Thanks in advance for any responses.

 

Correction- THHN

 

you could use it, but the next owner of your car will swear at you.

Use the more flexible automotive wire, for wiring a car!

 

It's a budget build. Would you advise against using it for now just to get it drivable for the summer. I plan on getting a quality wiring harness as time allows.

 

I would never use it in a car, but I guess I'm weird. I wouldn't use wire nuts in a car, either.

Like I said earlier, you can use it if you want. Beware it won't bend easily.

 

A Rebel wiring harness is in the $200 range. You're gonna completely wire the car twice to save $200? Spend the money, do it once, do it right!

 

I've used it plenty of times. Yeah, it's stiffer but will form just fine with a bit of work. I installed literally miles of the stuff over the years I worked and had no issues making it look 'neat'. It's actually a considerably tougher insulation compared to 'automotive' wire. Do use good strain relief at all splice/terminations.

The downside is color choices are limited, so troubleshooting later can be difficult. Some write-on heat shrinks can go a long ways in helping with that.

 

Another consideration is that 12 AWG is kind of large for most of the wiring in a car....larger is ok electrically, but can be a pain for installing it, and connecting to smaller wires and devices. I prefer using the appropriate size wire for everything.

Yeah, I have taking PO wiring out of cars that was done with house wire, and it was not pleasant.

 

THHN isn't 'house' wire, it's used in commercial/industrial. The 'vintage' type wire that used to be used in cars is very similar to the old TW or THW wire that was pretty easy to damage which is why it fell out of favor.

I will agree that using heavily oversize wire will make terminations difficult in places, but I'm also not a fan of aftermarket harnesses as they cut the same corners that the OEMs did. And then sell you 'relay kits' to fix the corner-cutting....

 

I wish I could recall where I saw new bulk copper auto wire for very low prices in the last few months.. But there are so many places to find low cost auto wire, tag sales, flea markets, or you can even salvage wire from newer cars that have multiple long runs to the back of the car, and it's in looms so it looks new and is still flexible when you take it out of the loom.

 

Since it's double insulated it's a pain to strip sometimes. 45 year electrician in a power plant and I'm sick of that shit.

 

You need new strippers... LOL...

 

Yeah, I suppose.



The main problem, to me, seems to be how few strands it has.

 

Stiff wire with few strands is unsuitable for environments with movement. Vibrations may cause the strands to break over time, while a wire with more thinner strands would have been fine.

 

When I rewired my '57 Chevy (back in the early '80's) I pulled a complete harness out of a 65 Belair and it was a very inexpensive easy to do wiring job. Even had all correct GM color codes! Imagine that!

 

And I,d bet what you have is all one color,,,,,BAD <<<DO NOT USE IT...check out Rhode Island Wire...
for proper wire available in all colors

 

Yes, it's 'coarser' than 'automotive' wire, but I've installed plenty of it on equipment that shakes, rattles, and rolls far more than any car ever would without any issues as long as you did a decent job on strain relief. I've put miles of it in lumber mills, and if you subjected a car to the conditions some of that gear sees, you'd have a pile of scrap metal in short order... LOL

 

Dude, don't worry, THHN will work just fine. I've been using it for decades in all kinds of electrical installations...

 

THHN resists oil, sunlight,abrasions, but is stiff, I would not have a problem using it in limited auto applications where there is no flexing.

 

It's even fine in places where there's movement, as long as you strain relief it and leave an adequate 'loop' in the wire so it doesn't have to make a sharp bend.

It's actually the insulation that protects the wire from flexing failures, it's usually when the insulation breaks that the wire fails. That's why OEM crimps grip the insulation, not just the wire. Now I'll grant that the modern wire most harness makers are now using does a good job of this, but it looks even less 'correct' than THHN wire does compared to the old-style thermoplastic that came in during the '50s. The earlier rubber/cloth wire was good too... when it's still relatively new. But that deteriorates from heat/age rather quickly compared to plastic, which is why it disappeared.

 

If it's black and # 12 awg, I'd use it for running a negative around the car. I rewired my 52 with mostly 14 THHN and I did use a black 12 for the negative from the battery to the front terminal strips in the grill. Also to under my dash, and back into the trunk. One thing is guaranteed, if you don't ground well to the negative, you will have issues. Especially with the lights in the 50s Chevys. Unless your adding a lot of extra accessories to your car, I would go along with the fuse panel but just don't over install the circuits, just because you have them. Maybe you can trade the # 12 for some #14 and get a few different colors.

 

Several years ago I was at an auction of a marine supply place that was going out of business. I got into the bidding and won a couple large boxes full of marine electrical stuff, including a couple dozen rolls of "marine grade" wire. It is far and away the best stuff I've ever used. It is real similar to the stuff available at the link below. How many different colors do you want, they've got the entire rainbow....

http://www.bestboatwire.com/marine-wire/marine-primary-wire

 

Gentlemen, thank you for the input. My car is now running and I am headed to the courthouse in a bit for current registration. It's gonna be a good summer.

 

In some areas , thhn in conduit ,is code for residential wiring ,i.e. house wire ..

 

If I remember right, 12 wire needs a 20 amp fuse. So every wire will be 12 and every fuse in the fuse box will be 20 amp??? Buy a fire extinguisher...lol

 

Well, you don't need to use the max fuse the wire can handle just because it can handle that much current, a smaller fuse is perfectly fine.

 

This whole thread is typical of what I go through with customers and friends, "well, I got this stuff, can we use it? But this kit is only "$ insert price" I use american autowire products, only gotta wire the car once, never have to source switches or connectors, plastic plugs, nothing. Truth is, you can wire your car with any kind of wire you can find, any colour you like, and hopefully when you embark on that long awaited trip to bonneville in your hot rod, it don't catch fire in the middle of the night in the middle of bumfuck nowhere. Not fun watching all those hours toiling away building something over a period of years melt into the ground with no hope of getting your investment back. You'll spend thousands and hundreds of hours on paint and body, but only two dollars for wiring because you don't understand it? Good thing I don't understand paint and bodywork, cause I do understand a quality wiring job.

 

I understand the sage advice you and others have given. With two kids in college and a new house payment the car has already sat for years. Think I'll do what it takes to get it running with what I have on hand and drive it till it burns or the wheels fall off but I really do appreciate the input.

Sent from my LGLS991 using The H.A.M.B. mobile app

 

Not meant as criticism, wiring is one of those things that you don't see in a car and a place it's easy to skimp on, chances are....if you wire it good enough now, it'll stay good enough and over the years get added on to as needed. None of my cars ever caught fire because of shitty paint or a dented fender. Congrats on the new house, wise investment.

 

Proper use of fuses and proper connections will minimize the risk of fire.