I have a 1988 s10 Blazer. The temp gauge reads 0 when I start it. 2mins after that it shoots up to max. When I switch the car off the temp gauge slowly settles down to 0 again. Rev counter is stuck on 3 when switched off but works fine when running.

I changed the temp sensor and tested resistance on it before I put it in. Looked good.

Any suggestions on getting the cluster to function properly?

Thanks in advance