Is there a resource to check for wiring harness interchange between C3 years. I have a 73' -w- auto and AC and would like to know if any other years would work? (i.e. 74' or 75') Looked into new harnesses, but $1000 is out of the budget right now. What is everyone's experience buying used harnesses? I have the ability to test the connections, but don't know if I should just wait till I can afford the Lectric LTD new harnesses.

 

The way it was explained to me by the guys at Lectric Limited is that auto wire maufacturing techniques were changed around 1980 or 1981. Pre that, the wire was prone to breaking down, corroding etc about 10 years after manufacture. They reckon even if you buy a NOS harness that's been on a shelf and never installed, it will still be corroded inside.

Post 1980/1, the wire lasts for ages (I can't remember - sort of forever). That said, if you send them your 81/82 harness, they unwrap it, inspect it, repair it if they need to, then test it and rewrap it. Any damaged wires are replaced by the correct gauge and colour wire and they claim that their harnesses will pass NCRS standards. They refurbished an 82 dash harness for me and it looks fantastic - new basically.

Pre 81 harness they won't repair but they will build a correct one for your car (or already have them in stock).

My 2c is wait until you can afford a new one from LL. If you buy another old harness, you might just be replacing problems you already have, with even more problems...

Like I said, just my 2c

 

I just had a quick check on LL web site. What harness do you need? You're looking at a grand only if you replace every wire in the car

 

I went with a generic unit for a hotrod. In the middle of putting it in now. Actually mounted the fuse box in the compartment over the drive shaft tunnel.

Not for the person who needs plug-n-play and not for an NCRS candidate. But at $250 it's a deal and my car is so far from stock than an original harness would have needed a fair amount of hacking anyway.

 

That'd be me - I am electrically challenged

 

Just started the restore, and from what I've seen in the engine bay and dash I'm looking at replacing everything. I'd really hate it if the first week after I'm done everything goes up in flames!

 

Yep, burning it to the floor would sure ruin your weekend

If you're pretty handy with electrickery, I guess you could re-wire the car with a generic hot rod type of harness but IMO it'd be a $hitload easier with a repro harness where you KNOW all the wires are going to reach and that everything will plug into it properly.

When you think of all the work involved with a generic harness for the whole car, I reckon $1000 doesn't sound too bad...

 

SV, U need find a buddy who knows about electricals/tronics and solder some wires over there, these aftermarket harnesses are not all they cracked up to be...period...case closed....

you are far better off making you own, I realize you have short knowledge on this topic, but well, time to find help, or better yet...

get an electrical book, and learn the fun da mentals..and get a voltmeter to help you, then you can strip down the original harness and redo what necessary.....

I an old ET for years now, and so redid my own harness from ground up some years ago...just too many problems, I used all the stripped out wires of the original harness, and eliminated the bulkhead connector on the engine side, kept the front lighting side intact, more or less...

rear harness is intact, the under dash is all done MY way....

most of this stuff is just toooo damn old and corroded to be serviceable anymore...depends on the car, obviously...BUT from the stuff I seen, we dragging 35+ years outta cars designed for TEN.....

everything from rust to critters takes it toll...

 

Where can I buy primary wire in the correct colors and tracer colors? I want to rebuild my harness sometime soon, but I can't find a good source of those supplies.

 

The good part about using a Hot Rod harness, is that ALL of the wires are LABELed. The whole way down the wire it will say something like 'front right turn'. But, still not for the fait of heart.

On the generic harness I am using, all of the wires would have reached without issue if I had mounted the fuse box in the original location.

Since I moved it behind the seats the wires directly from the fuse box to the dash do not reach and need to be extended. But the headlights still reach fine. If you figure the fuse box is less than 1' from the rear axle centerline, that is a lot of wire.

Of course I'm going to run relays for the headlights & fan so didn't need all that wire anyway.

 

M & H Electric Fabricators has GLX wire in most gauge sizes color or combination (stripes). I would assume Lectric Linited and American Autowire (Factory Fit) would also offer this option if you want to fab your own harness(s).

 

I'm gonna tear out the dash harness this week and see if it's salvageable. I've got the "doc rebuild" schematic which is very easy to understand, kudos to them, and has the connectors illustrated. That makes it alot easier when your dealing with a car with half of everything disconnected. Wish me luck, I'm sure I'll have a few pics for the "Bubba's Work" thread. I thought about doing a Hot Rod harness, but then where do you get the proper connectors?

 

Hehehe, thanks for the confidence! I do have the fundamentals but I don't particularly like it. I am one of those naturally occuring "super earths" you see on Discovery type progammes. Electrickery will happily bypass a 1/16 inch gap between platinum contacts, to jump through 8 feet of cement and rubber to earth through me!

I did make my own harness for the electric headlights I fitted but what would probably have taken an eleco a few hours took me all day. It does work though, which I was pretty happy with!

I will have a go at some of the smaller harnesses but there was NO WAY I was going to try and fabricate a new dash harness - there's enough wire in one of those to reach from here to the bloody MOON and back!

 

mrvette! when you redid your dash harness did you replace any bulb holders and if you did where did you find them?--thanks---john

 

This is what I found when I pulled the dash last night! That's the headlight connector with an extra jumper?...I think...it looks like a fuse to me! Could someone please let me know where Bubba lives, I want to slap him!!

 

AS I recall.....I just used the original bulb holders, took the long gray pigtails, soldered them all together, brought out one gray wire to the white Radio shak (GOD I HATE THAT DAMN JUNKSHOP), BUT junk wins every damn time.....I got a MOLEX white plastic connector with pins...used them extensively in '70's TV sets....etc....they work ok, and under dash are protected, so weathertite is not necessary....
and run all the bulb/other wires though that plug...it's neat and easy...

I run all the other wiring up and over, tiewrapped up top to the steering support, and extra wear insulated...so it's separate from the dash pod....since the tach is like a '75+ electric now, I just have the one speedo cable to disconnect, ans since changing out the tranny, THAT is routed under the carpet/padding up top and through the tunnel with a ~3/8 hole and into the tranny...simple....dry, no grease, no sweat to pull it rearward with the dash pod....and nothing through the firewall there, hole sealed off...OR I used it for wiring...
I eliminated about 1/2 the large square plug on the bulkhead connector, the only part function there is the front lighting section outboard 1/2 the heavy current crap is all direct wired....
I stripped back all the original harness, finding the original wires were easy long enough when I re routed it all MY way....must have a 4 gallon milk box/container full of left over wiring....

I also eliminated all that start neutral/gear clutch safety crap...my car is proudly completely totally de NADERIZED.....you flip that lever it goes into gear, you move that lever when it's running, you just did something rong....learn to drive it, damnit....it's like a hold tyme hotrod...no interlocks, no safety switches, no bull crap...

I used a burglar alarm magnetic switch for reverse posisiton sense with a relay to light the bulbs....sneaky...I did want backup lights...

there is NOTHING stock about my car, nothing, not nuttin,...from wheels to roof, (when the top is up).....

 

I have a different perspective on it, in my opinion and experience, a used wiring harness can be quite suitable.

I've seen/used wiring that is quite old but entirely adequate and safe (like my '59 Pontiac). Most problems/potential problems are obvious, and usually are at terminal ends attacked by Bubba.

If you can find decent used harnesses (unmolested), I think you will save a lot of money, and have something that looks and fits best.

Steve

 

I don't know much about Lectric Limited, but the information quoted above is not accurate. The Packard Electric Division of GM made all GM harnesses. Both the basic materials (wires, terminals, connectors, harness tape) and harness assembly was done in Warren, OH until the early 70's when Packard opened the first of four plants in Mississippi. After that time, wire, parts and assembly could have been in either location. Assembly in the late 70's and later could also have been done in Mexico, but cable was made only in Warren, OH and Clinton, MS.

I worked in various engineering and management capacities in all the cable and plastic molding plants in both locations from 1968 through 1984. It is true that changes occurred over time - usually to address the ever increasing temperature inside the engine compartment. Wires subjected to heat were migrated over the years from a PVC (thermoplastic) insulation to a cross-linked polyethelyne (thermosetting) material. Connectors tended to migrate from polypropylene to nylon.

The wire was always pure copper, drawn from rod and twisted (bunched) into mutiple strands. Twenty gage was seven strands as was some 18 gage. Larger sizes were composed of more strands. This didn't change while I was in the field and when I had a friend give me a tour of the MS plant a few years back, it still had not changed. Only the machinery was newer and more efficient.

Terminals were always a problem. Moisture would cause them to corrode with associated electical connectivity issues. Most terminals were made of brass. Those that were going to be exposed to the elements (i.e. not inside the cabin) were plated. Connectors evolved over time becoming more complex is design, always to combat moisture and corrosion. Again this was and I'm sure remains to this day an evolution. Certainly not a revolution as suggested by Lectric Limited.

The one area that I might agree with Lectric Limited is with battery cables. At some point in the 60's copper became so expensive that Packard started using aluminum for battery cables. It wasn't simple aluminum but 'copper clad' aluminum. Copper clad aluminum had to be larger in size to carry an equivalent current, but it saved money. This went on for about a decade - maybe longer.

In about 1972 I was asked to figure out a solution to insulation 'sink holes' in cross link battery cable. I won't bore you with the details surrounding these insulation holes, but it was an expensive defect. Engineers had tried lots of things to fix the problem, all had failed. I worked the math and found that the relative difference in cost between copper and copper clad aluminum had eroded so badly over the previous decade that the solution was to go back to copper. That took about two years as terminals and various tooling and fixtures had to be changed. The bottom line is that battery cables again became all copper about 1973-74. (This information about copper clad is across all car models. I can't confirm that copper clad was ever used on a Corvette. To me it's doubtful.)

Copper clad aluminum was definitely guilty of corroding from the inside out. Copper clad aluminum however was never used on any wires in a wiring harness - only in battery cables.

 

The bidder you beat out earlier today on the used 1974 Main Dash Harness (GM calls it an Instrument Panel or IP harness) was me! I had no idea until I read this thread tonight.

That harness looks real good in the picture. It will definitely work for you. Be aware that not all IP harnesses are the same. In 1979 the basic IP harness had about 180 wires in it but there was a second harness that supported options and it had over 200 wires. I don't know the numbers for the '74 model but the principle would be the same.

 

I can confirm it - my 77 had copper-clad aluminum battery wiring. The AC Delco replacement wires are pure copper, and a helluva lot heavier, even if slightly smaller in diameter.