I have a funny trouble with my temp gauge. It reads fine when the car is stopped but goes to zero when the car is moving. I've checked my grounds, cleaned my connections and checked my fluid levels. I've used the search and didn't find anything I haven't tried yet. Any ideas?

Do you have a thermostat?

yes

Ok, it could be stuck open. My car did the same thing when I bought it, no thermostat.

Does it immediately spring to 0, then jump back up again when stopped, or take a few seconds? How hot is your heater during the winter when you are driving?

Get a wiring diagram. Get a fsm so you know how the gauge comes out & where the wires run. (You didn't specify what year.) Test continuity through all connectors. Try to replicate then repair.

It goes to zero after a second at most. I don't ride it in the winter so I dont how hot the heater gets. Too much road salt here in the winter. My Zs a 77 BTW.

Could be a bad sender. Touch the sender wire to ground and see if the gauge goes to full scale w/ the ign. on.

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Rusty but running.
Polish cell phone and two tubes of Aluma-seal.

And, now we are historic.