.......on my '73 Roadrunner, with Rally guages, my Temp guage isn't working. Here is where I am at, all of the other guages work, all the lights, etc., there is a pulse to the sender (when I check it with my test light) and the sender is new. It is a new engine. Before I put the dash togther, I checked all the guages with 3 volts. They all moved. Is there something I am missing? Replacing would be a major pain, I hope it isn't the guage itself. Thank you guys.

Have someone watch the gauge while you breifly ground the wire at the sending unit...If it rises then the problem is with the sending unit....The fact you have a pulsed signal points toward the sender...

BTW don't leave the sending unit wire grounded for long it can burn out the gauge...

I will try that, thanks. I also had wire wheeled the threads to the sender, and I made sure that I did NOT use any sealer. If the water level was low, would the sender not do anything? Or would it make guage at least start reading?

Sender must be in water to read. It won't read air temp.

I just went out and tried grounding the sender wire, there was no action at the guage. Then I tried the test light again, and now the pulse is gone. It was pulsing, now it is not. So where is that little devil that makes it pulse?

Find the connector and terminal number on the bulkhead connection and check the connectors.

The pulsed voltage comes from the voltage regulator, but if it is bad the fuel and oil gauges won't work either.
If you see the voltage pulsing on both sides of the gauge terminal, then the gauge is good and is getting power from the instrument panel regulator.
Because grounding the sending unit (with power on?) did not show a reading you have a bad connection or broken wire between the gauge and the sending unit. I would connect a probe to the bulkhead connector cavity for the sending unit and chech for the pulsing instrument VR voltage or just connect to ground to see if the gauge responds. If the gauge responds the problem is between the bulkhead connector and the sending unit. If the gauge does not respond the check the connection / pins on the dash harness. Also check that the dash circuit board does not have a break in it.

Well, it took some doing, but it ended up being (2) problems. A bad wire at the connector, (I re-soldered it) and the sender itself. The pulse is back, and when I ground the repaired connector, the gauge goes up now. But still nothing when attached to the sender, so I am going to get another sender. Thank God I don't have to replace the gauge, it really does not look fun in a '73!

Signs of life for the first time from the guage today, I installed the new sender and it seems to be doing something. I think it is still low on coolant now, so I am going to add more and try again. But it is working! The "new" non-working sender I replaced was aluminum, if that helps anyone. The one I installed today is a Mopar one, and brass.

You could ground the sender body and put it in hot water and see if you get a reading. Check the temp of the water with a thermometer and compare reading with gauge in car.

Thanks, I will try that if bringing the water level up doesn't work.