Trying to get my 72 up to date after years of sitting. Most of my gauges don't work. The wiring has been tampered with and I'm not good at wiring/electrical problems. I don't believe the gauges have been tampered with and I don't think they're the problem. Gauges that don't work are the water temp, battery/charging, oil pressure and fuel. Remarkably the clock works like a charm.

I started trying to get the temp gauge going. It has a tan/brown wire attached which goes into a harness with other wires at the firewall. From what I've read in the shop manual the wire should be green. There is a green at the gauge but it disappears into a harness under the dash. Should I splice it and run a wire to the sending unit?

While tracing wires I found a (semi melted) flat connector at the firewall with two blue and two brown/tan wires. Where the other end is I have no idea; nor what it does.

Anyway, these are for starters. Thanks in advance for any advice or help.

 

Check your grounds first. Then check to see that you're posting it in the appropriate sub-forum.

 

Exactly !!! C3's are notorious for faulty grounding. Unlike most cars the ground can happen on body panels.
C3 Vettes have plastic body panels. All circuits on Vettes have hot wire and a ground wire that goes to a
single ground lug on the frame in the engine compartment.

BTW, nice break from the political spew....

 

Thanks for the replies! Should I re-post and where should I post?

 

Ask a mod to move the thread for you

 

Try here. Good luck.

https://www.corvetteforum.com/forums...performance-3/

 

Almost as badly as C5s

 

If your grounds are good, you'll then want to check all the wiring to them. If it's been sitting for a while you likely have mice in there and for whatever reason, those bastards love to eat wires.

 

Different vehicle but also a 72 Chevy, C10 Truck. Had numerous wiring issues and got tired of chasing down bad circuits and trying to figure out what someone else did. So, I ripped all of it out and installed a completely new vehicle specific harness for everything. Nice thing about that approach is all of the old style glass fuses were eliminated and replaced with the more modern mini-fuses. Also of benefit, is getting more usable circuits than the original fuse block had. It took some time, but when done I was no longer worried about shorts and things burning up.

These new harnesses are easy to install, because each wire is color coded and labeled for what it is, plus the kits come with complete wiring diagrams that show you all the circuits and the correct connector to use for each circuit. They also come with all the OE style plastic couplers, to plug in the different components once a circuit is ran and terminated. The hardest part is just routing the wires and doing the wire management, so everything is protected and secure. Just like anything else, you approach it one step at a time. Looks intimidating at first, but if you follow the simple instructions and approach it one step at a time, anyone with some vehicle and mechanical experience, can do this.

Another benefit is when you are done, you are far more familiar with your electrical system and you are who ensures everything was installed and connected correctly. If you take your time and do it right, you will have a rock solid electrical system you won't have to worry about again. Those old harnesses are prone to problems because lets face it, they are almost 50 years old if original. They have deteriorating, the wires are brittle, including the insulation on the wires and some of the problems are hidden and out of sight. That is exactly what I found when pulling all the old wires out, there were problems I would have never seen. A new harness addresses all the issue in one fell swoop.

As far as the gauges, I don't recall if the oil pressure gage on the Corvette was a liquid gauge like what is was on the truck, or an electric one. To get rid of the liquid gages, I went with a whole new instrument cluster that was all electric, including the speedometer. Most of these new instrument cluster kits come with everything you need to do the conversion on your vehicle, so that is always an option if you choose to go that route. Don't know for a fact, but if I were guessing, someone is making modern gauges for the car the look like the originals.

One of the things I did to address the grounding issue, knowing I was going to be replacing other components in the truck, is I ran a dedicated ground feed from the battery into the cab and created a ground block or connection point. Also ran the main ground to the engine block and the normal grounding straps to the body. Considering the body on your car is fiberglass, a grounding point inside might be of benefit for you as well. For the tail lights that used a body ground, I ran new ground wires all the way back to ensure those lights would have a solid ground as well. Was not going to trust the body ground alone with new led lights. New components like the Vintage Air HVAC system, require a direct ground from the battery, so having the grounding block inside the cab was nice.

Don't know if that helps but there is my half cent worth..

 

Hey! Is this the PR section or C3 section?

(just wanted to get back for those who come here bitching about "where's the Corvette talk?!?!")

 

WOW!!!! A P&R thread where everyone agrees.

 

Don't worry, it will soon be moved and everyone can go back to their corners.

 

Let's do one problem at a time.

 

Thanks for the info and the pics. Trying to work my way through. I think I found what the flat connector with the four wires (2 blue and 2 tan) is for: Automatic transmission step down. Probably just a stray plug in the standard wiring as I have a 4 speed. I have a few things to test/go through and I'll let you know what happens. Thanks again.

 

Wires and corrosion can be a tricky issues. I had a wire connection to a light that I inspected. The two wires were twisted together and taped. After inspecting the connection I found EVEN with the two wires twisted together, they were not making contact. After years of sitting, corrosion had developed between the wires. Tracking down grounding and power issues make sure you really check and clean all connections.