Hey everyone. After 30 years of a c3 I finally picked up a 78 corvette this weekend. The body/frame is in good shape and it runs great, but the wiring is a mess. I pulled the dash apart last night and found a lot of harnesses that were not connected to anything. While I wait for my service manual to arrive, does any one have any idea where these should go?

Center gauge area


Center gauge area cont.


Under drivers dash near fuse box



Also, in what might be the weirdest thing I've seen in a while, when the turn signals (which don't work currently) are turned on, the tach (which seems to work fine otherwise) raises by about 1,000 rpm. I'm guessing this would have to be a short in the circuit board behind the dash connecting the turn indicator and the tach circuit?
Sorry in advance, I know I'll have a lot of questions. I've been working on cars for years but this is my first c3.

 

I believe the red wire with the single white connector goes to the cigarette lighter. the connector with the yellow, red,blue, white wires is part of the radio harness i think. I just swapped out my radio in my 78 so I was just in that area a couple of months ago.

 

While your waiting for the service manual this might help.

http://www.vetteprojects.com/bmv/mis...tte%201978.pdf

 

The light bulb is for the automatic transmission plate to light up at night. a couple of them could be for power windows or door locks.
A service manual would definitely be useful. It will have location of the plugs in addition to the colors

 

The service manual will have limited value of wire color coding and where they go. It will identify component location if it is not an assembly...assembly part numbers are clusters of parts.


I've had my 78 for over twenty years and have enjoyed it thoroughly. It offers a nice contrast to vehicles after that point in terms of simplicity as a car guy that likes to keep his skills up!

Having said that the absolute best electrical schematic is a 11 x 17 1978 specific-schematic published for GM with an image of the Pace Car on the front page. It combines three aspects that other schematics do not offer

1. Color-coded wires
2. Component location
3. Circuit Operation

I have a couple but I got one at Carlisle from a vendor who specialized in Corvette documents. The other I got through eBay...it's a cleaner one that the first. An image of the cover is below

I also use a color-coded wire schematic by Olson Engineering (Don Olson) that is a one-sheet laminated schematic that I use when I need to trace a circuit through several different wire harnesses...such as speaker wire connections.

Both are the tools needed, among others, for electrical troubleshooting. I also have a dash wiring harness, used from a Pace Car that I also used for tracing dash wiring issues. But you get the idea.

Hope this helps!




I Just googled the title and came up with one on Ebay for $35 plus shipping! Get it!

 

Dude!...you are my hero!...been looking all over for something like that. Just picked up a 78 project car for my son and me. It has gobs of electrical issues.

thanks!!!...JP