mckenzie;

What wire going form the "sensor" to the gauge? Be advised, on BOTH of your Amazons, those are not sensors nor are they wires connecting them to the gauge, they are an end fitting (soldered closed), on a capillary tube filled with ether. Grounding has ZERO to do with your temperature indicating system. The ONLY thing electrical about it is the light at the gauge which lights it when lights are on.

I wouldn't want you to be (another) owner who thought he could just "unplug the connector" when removing an engine. Compromise the sealed system ANYWHERE along the way, it's toast, and you'll be looking for a replacement.

I stand by what stated before: If the gauge reads at all, the entire system is FINE!

Cheers