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New versus old wiring

5K views 59 replies 23 participants last post by  68Cpe307 
#1 ·
I am having a hard time deciding if I should rewire my whole car or just stick with the original wiring that is in it. The car sat for over 40yrs and was only drove for about 7. I havent seen anything wrong with it but I am debating if I should just go new. What do you guys think? Incase you guys dont rememeber its the 68 SS.

 
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#3 ·
Unless you can see the insulation deteriorating or the wiring has been hot and started to melt the insulation, then you should be o.k. You may find that the copper in the wire has started to turn black, usually on the headlight & other high current circuits. If you install headlight relays and a starter relay to take those heavier loads off your dash wiring the original wiring loom should still serve you well.
 
#4 ·
On my 68 the deciding factor was the condition of the fuse holders. They were all pitted and that had me concerned. I decided that since the dash was out I would install a new harness and all new switches. It's about to go back in, in the next couple of days. One suggestion I have either way you go. Consider running a direct ground wire from one of the small bolts on the back of the dash where the bracket that holds the ignition switch bolts to, to a good frame ground like the parking brake bracket. If there isn't one there is only a ground at the top left mounting hole clip.
 
#9 ·
I've worked on hundreds of classic cars. Most of the time the wiring is so butchered it's unreal. Plus we are talking about 40 year old copper shielded wiring. Granted gm had the best wiring (ford the worst) I still would not put a dime on my own money into a car that I had to worry about wiring issues. It just makes sense to change it. People change engines all the time when it's not needed. Why don't people do wiring? I guess it's more fun to say yeah it's got a 450hp big block rather than yep I got a all new wiring harness. But to me it's just anothe thing that should be done when restoring a car. Like my grandmother always said "your getting a bath whether you need it or not"
 
#10 ·
you say you worked on 100's of classic cars. how many of them had a wire fire. I do say replace them if they are all cut up and messed with.
 
#16 ·
One, it was a 66 ford mustang. Car was brought to me a charred mess. Fire started behind the dash burned the car then took out the garage with it. Thankfully the garage was not attached to the customers house. He paid top dollar at a auction and assumed it was a good car. $45,000 worth of damages plus whatever his garage cost him.
 
#11 ·
If the wiring is not cut up or just plain visibly bad, I wouldn't replace it. GM had good wiring back in the day. Some of these kits on the market cause me concern (name brands) The wiring is much smaller and just looks weaker. The only "cool" thing in my opinion is getting away from the glass fuses--- but they work just fine.

I've done a couple complete rewire kits where you have to use your own fittings on the ends of the wire. From what I know about wiring, If you're not a professional solderer, crimping is best. Who wants a bunch of crimps in their harness? Now-a-days I just replace the section of harness that is bad with a quality repop or make my own.
 
#17 ·
I've installed painless, m&h and aaw kits. You get what you pay for. Painless is a descent kit for the money, it's also the cheapest. Wire size is sufficient and it's easy to install. I haven't used a crimp connect in years everything is solder and shrink wrap. However even the expensive kits need to be reworked and altered to work
 
#18 ·
I built a SS 454-70 Chevelle Sta. Wgn. in 2002. The under-dash and under hood harness were from my one owner 70 SS 454 El Camino. Cleaned every connector,did some minor repairs, Dielectric grease on EVERY connection.
The 42 year old used SS under dash and under hood harness have been just fine since 2002 or 10 years. It was not chopped up. If is NOT CUT UP, Clean it, Inspect for broken loose wires, And reinstall.
I use dielectric grease on every connection. This may be right or wrong, I do not know????? So far the FORTY TWO year old harness (under dash & under hood) are still working. No fires yet.
Bob
 
#20 ·
If electric fans, high output alternators, electric fuel pumps, big stereos, etc are added to a car and not wired right, I could see the factory harness not holding up. They weren't built for that. Other than that the factory harness is great and will work with anything added if the new add ons are wired correct.
 
#21 ·
When adding all of the high amp draw accessories I use a separate wiring system. A small fuse panel is added for the additional circuits, protected with fusible links between it and the battery. Wires need to be of proper size and loomed to protect them.
As said it is the hack jobs that cause problems. The worst hack job I have seen is the 57 Bel Air I am now rewiring. The owner paid a shop to install an AAW harness. None of the connections were made properly. There many places of wires just twisted together and covered with black tape. Hacks can mess up anything, in this case it was all hidden under black tape, but all those fat spots in the harness were a dead give away that something was not quite right.

Here is a gauge cluster I wired using factory wire gauge size and colors for each circuit, soldered connections and a weather pack connector. It takes some time to do it correctly but it should never need to be redone.



A schematic was also created in case trouble shooting was necessary in the future.
 
#22 ·
Ok well I went by the shop to look at the wiring of the Chevelle and saw the clips in the fuse block that hold the fuses in are in fact rusted. So looks like I am going to have to replace it. So if I got with and aftermarket wiring system what are the recommendations? I have used Painless in my Mustang and yes it was a pain in the A$$. But what if I replace the wiring with the same style? Like if they remake the original style. So replacing is for sure but now which harness?
 
#24 ·
The clips can be cleaned but if you go after market American Auto Wire would be my recommendation. Easy to install, uses OEM colors and connectors all the circuits are well marked.
 
#26 ·
Usually it is just surface rust. If it has pitted it would be best to replace, either the panel if you can find a good one or with a new harness.
Naval Jelly will remove it, maybe a flux brush could be used to apply it and make sure it is all rinsed off.
 
#29 ·
I agree on both sides of the table...

As we were restoring our 71SS454 Elco we had the dash as well as everything else out. The original SS dash housing was so butchered with holes and cracks everywhere that we purchased a repro dash housing(I know, I know). As I was cleaning the original dash harness, although not cut, I noticed hard brittle wires everywhere especially near the fuse block. I purchsed a high quality dash harness from M&H as well as a front lamp and engine harness but left the body and all other harness alone and intact as they were not worn or butchered. The M&H kit was as close to "plug and play" as you are going to get IMO and installed perfectly utilizing correct GM style connectors and required no modifications. The only mild gripe I have with M&H is they dont label each wire for the component it goes to as their competitors do(then again M&H prides themselves on OEM resto quility and GM didnt label theirs either)

Caveat 71-72 connectors and I would assume ALL harnesses nade by them used were from the latest GM revision for that model year and optioned harness so they may not be exact to what you have as these years were pivital. Since yours is a 68 model year I would assume it would probably be a fairly straight forward R&R as well.

We probably could have left dash harness alone but dash was out anyway and all new wiring from dash forward makes me able to sleep at night as well as feeling more at ease when taking car out for long drives.

Marc S
 
#33 ·
In this case the car sat unused for a very long time, this would tend to preserve the integrity of the harness. If not chewed on by rodents it should be fine.
Billy I'll PM my cell number and let you know next time I will be in Phoenix.
 
#34 ·
Well I made my decision guys. My father told me something about the car I didnt know. I guess when it sat for some of those 40yrs in Flagstaff, pack rats got into it at one time so who knows what they were chewing on. Plus the clock in the dash had a short and my grandfather did something to it to get it to keep from killin the battery. So a completely new system now, just have to decide which one would be best. American Auto Wire harness has alot of stuff in it I dont need like the power windows and so forth. Only thing modern I want in it is HEI, electric fan and cd player. Painless just has a universal system for GM and I have used them before in my Mustang and it was a pain in my behind.The M&H I would have to piece together and have no clue, I am still a beginner when it comes to wiring. Painless is the one I am most comfortable with but it is a pain. So what would work best based on just wanting the original stuff and those few modern comforts?
This is what I can get locally
http://www.haywireinc.com/index.cfm/page/ptype=results/Category_ID=2/home_id=-1/mode=cat/cat2.htm
 
#38 ·
I have used a American Auto wire harness kit, and this is quite easy to install. The cables is colourcoded and named/tagged. The kit is also prepared for some "modern stuff", but you don't need to buy all the extra harnesses. You would still need a "professional crimper" for all the fittings, and you have to be aware that the lamp sockets is not sealed like the original. Sure thats not a problem in AZ, but here at the western coast of Norway it means a lot.
The kit also have extra length of wires at the front harness, so you can route the wire in the fenders if you would like to clean up your firewall, and some other benefits.
 
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