Ive searched old threads and trying to make sense why all of a sudden when I put my car back together the only thing that doesnt work is the temp guage and I never fiddled with it or the sender. I do recall when hooking up the alternator wires, the pos. wire touched the block for a split second and I got a big spark but that was all. Everything else is working, Voltage at the horn relay is 14. The guage always worked great, slowly rising and settling in at just under half mast or center unless running the a/c when it went a little higher. Now it sits at the left edge slash mark and wont budge. I grounded the sending wire after removing it from the sender and the guage still doesnt budge. Could I have blown the guage with the temp flash of the Alt. wire going to direct ground? :(

I can't imagine the event would damage the gauge.

Take the wire off the sending unit, using a voltmeter, measure available voltage to ground. Should see 7 volts(?), but not battery. Resistor on backside of gauge cuts down voltage. If no voltage at wire, then it is either the gauge is bad or the resistor is bad, or no battery voltage going to gauge to begin with. If you can, place ohmmeter probes across gauge only terminals, ohmmeter should show resistance, meaning current can flow through gauge, and should see temp gauge needle deflect.

With ohms selected on meter, wire still disconnected at sending unit, measure ressitance from terminal to engine ground. Should be a high resistance at room temperature, say 6K-12K ohms. As water heats up, resistance goes down, 180*F might equal 180-200 ohms, something less than 1K ohms.

I had time to check the lead wire after pulling it off the sender, I get NO voltage at all there. Ive not yet pulled apart the guage package in the console, but I notice that when I turn the key to off, the temp guage goes up to the 2nd 'tick' above full left setting. When I turn on the key power, the guage dips down to full left or cold position. Not sure that helps isolate the issue but thats what happened. Might get to pull the guages this weekend.
:(

I notice that when I turn the key to off, the temp guage goes up to the 2nd 'tick' above full left setting. When I turn on the key power, the guage dips down to full left or cold position. Not sure that helps isolate the issue but thats what happened.

It reads like the gauge may have become a residual magnet already, meaning it has its own magnetic field, which would oppose any electrical induced field for indication. I would keep this as a last resort if troubleshooting the gauge otherwise and no other fault is found.

Disconnect the sender lead and see if gauge does same motion. If it does, then gauge I think, would be bad.

Hopefully, it'll be something simple.