Temp Guage issues

First, does the fuel gauge work? They are fed off the same "voltage limiter" a sort of almost voltage regulator that feeds fuel, temp, and if you have it, oil pressure gauges

If the fuel gauge works, the "quick test" is to remove the sender wire, clip lead it to ground, and then go in and turn the key to "run" and watch the gauge. In a very short time it should head quickly to "hot." Don't leave the key on for long, just see what it does.

If this does nothing, it could be the wire is broke right inside the connector, a bad connection going through the firewall, or problems at the dash group connector, or the gauge itself.

Next step is to pull the dash cluster. Use a continuity lamp or meter to check the wire itself.

If that's OK, try jury rigging the dash --plugged in, grounded, and ground the sender wire where it comes off the gauge. Then turn the key to run as before and see if the gauge goes up.

If not, check with a lamp for power at both fuel and temp gauges.

If grounding the sender side of the gauge doesn't cause it to deflect, and if it's getting power from the "limiter" at this point it's probably the gauge itself.