cooling problem

The temp gauge relies on the secondary power ground for its return signal path. If the ground is bad, the temp gauge will read high. Sometimes turning on all the electrical loads will cause the temp gauge indication to increase and then decrease when you turn them all off again.

The secondary power ground is between the back of the intake manifold and the driver's side firewall. It is often missing or loose. It supplies ground for the alternator, A/C compressor clutch and other electrical accessories such as the temp gauge. Clean the places where the ground strap mounts with fine sandpaper so that they are clean and shiny. This is cheap, easy and is a good fix for gauge problems.

JGT said:

Well I looked today, and it is there. Why isn't it your standard power wire? It's one of those braided straps. I was thinking I should replace it with 12g wire. Do you think that would be better? 12g should be big enough right?

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No need to contemplate replacement. Simply add another cable to augment the OEM version. When I add engine grounds, they are 4 or 2 AWG or a large strap.

Good luck.