76 dart temp gauge problems!

God, no. I guess I assumed you had more understanding. The gauges are powered NOT from 12V, but from the output of the "voltage limiter" known by a couple of different names. ORIGINALLY this was an electro-mechanical device like a flasher.........rapidly pulsed the 12V supply on/ off to produce the same effect of "about" 5V. So all replacement solid state IVR devices are 5V output.

You either need to fix or confirm the PC board is good, install it in the cluster, or else devise a method to produce 5V to the gauge. Variable power supply, etc.

CAREFUL!!! You can easily hurt/ murder these gauge units!!!

Frankly, I would inspect / fix the PC board, and install the IVR and gauge (s) onto the PC board, and test it that way.

You need 12V to the appropriate pin, ground to the PC board common, and of course a sender test resistance.