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

OK, sounds like it SHOULD be installed right.
- The other limiter is suspected as kaput and is putting a full 12v to the gauges and so that is why they went full scale. Whether they are damaged or not now is the question (as I think you know).
- The output from the stock limiter and the RTE IVR4 is a pulsed 12 volts. It goes from 0 to 12 volts and then back to zero. It is 12 volts about 15-20% of the the time, and 0 volts the rest of the time. This is done to mimic the power available in a 5v system. This gauge design originated when car systems were 6 volt systems.) Your meter will register this pulsing differently depending on the meter. Do you have a digital meter, or one with a needle? If the meter reading wiggles up and down then it sounds OK; it is hard to tell with the way that every meter type responds differently to this pulsed voltage.
- The test described above with the resistors is what the gauge tester would do. Buy the resistors and some test wires with alligator clips to hook it up and go to town testing gauges. The whole deal will cost you a few bucks and you'll be an expert in no time. But you have to have a known good working limiter or a 5 volt source.
- Can you sneak a mirror up behind the panel and see the IVR4 LED light reflecting off of the circuit board?
- Otherwise, take the IVR4 out and use some test jumpers. Connect the 12v input to battery +, the ground to the battery -, and see if the LED is blinking. If not, then jumper the output to the temp sensor on the engine and look for the LED to blink. One thing I realized I can't remember 100% is where the 12v input is on the IVR4. I think it is the spade lug closest to the middle; looking at the RTE limiter FAQ's page confirms this. RTE Limiter Faq - rte
- If you can't figure out if the IVR4 is working or not, then use a 6 volt lantern battery, or set of 4 1.5volt batteries, as a temporary test source for in-car or out-of-car testing. The 6v battery would hook to the cluster where the tab on the IVR4 that is furtherest away from the ground tab connects. If you are hesitant, I would try this out-of-car with the spare gauges and resistors first.
- Sorry I don't have the time to diagram it out for you.