So I've been doing a lot of digging into the issue where temperature gauge maxes out as soon as the ignition turns on and gets pinned at the top. I replaced the temp sensor thinking that was the issue but it wasn't. Then I looked into the temperature sending unit located between cylinders 1 and 3 on the drivers side. I bought a replacement sending unit, however after connecting up the new unit I still got the same problem, temp gauge still pegs at the top on startup.

Worried there may be a ground in the wire running to the sending unit, I decided to run a new wire to the sending unit by finding the dark green wire shown in this diagram.




After cutting the green wire from the wire loom located near the firewall and soldering a new wire to the connector on the new sending unit, I STILL got the same problem upon startup.

My next step is removing the entire instrument cluster and looking for broken wires which could be causing the grounding issue. I really don't want to do that because it's a huge pain in the a$$ for just the temp gauge, and I thought I might try the forums and see if you guys have run into and fixed this problem before.

This is what my old sending unit looks like.




and the new one I bought is the fourth one in this picture (with the spade connector)



I have a 1988 Iroc-Z Camaro, 305 ci. Any help is appreciated!

 

I bought a new gauge and it fixed my issue. The new gauge doesn't send the needle "full force" to the max position when starting. It seems to limit it from doing that. I haven't had the issue since.