65 Valiant now gauges go full when ignition key turned or running

Sorry for the frustration..... Is the LED on the bottom (connector) side of the RTE limiter flashing when the key is in RUN? Is the case of the RTE limiter grounded to chassis, directly or through the clusters ground? Is the cluster properly grounded as you try these tests? The voltage at the IGN teminal is OK. And I am assuming this is the IVR 4 RTE model; is it?

How much voltage do you see with your meter at the end of the temp sensor wire with it disconnected from the sensor, with the RTE unit installed, and the key in RUN? Makes sure the case of the RTE limiter is grounded to the proper traces on the dash circuit board, and that the dash I may be jumping up and down. Do your best to describe the readings.

If you want to test the other gauges outside of the car:
1) Use a 12v battery as a power source.
1a) To check your power source and setup, connect the RTE limiter to the battery with the 12v going to the + terminal and the case of the limiter to the -. See if there is a pulsing voltage at the output terminal of the limiter and that the LED is blinking. Then disconnect the limiter for now and.....
2) Buy 3 resistors from www.mouser.com. All 3 should be 1 watt rated, and their resistance values are 10 ohms, 22 (or 24) ohms and 72 ohms. These will be used to create your own gauge tester.
3) When you get the resistors, connect the RTE limiter to the battery with the 12v going to the + terminal and the case of the limiter to the -.
4) Connect one terminal on the the spare temp gauge to the RTE limiter output and the other terminal to one end of the 10 ohm resistor. The connect the other end of the 10 ohm resistor to battery -. The gauge should slowly move to H (hot) or close to it.
5) Replace the 10 ohm resistor with the 22 ohm one and see if the gauge goes to about halfway.
6) Then connect in the 72 ohm resistor and the gauge shouldread C.
7) Repeat steps 4, 5, and 6 with the fuel gauge and see if it reads around F, 1/2, and E in that order.

If you were close to Waynesboro, VA, I'd lend a hand.