Instrument cluster voltage limiter.....?

Justin Plant

Well-Known Member
Nov 11, 2021
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Moneta, VA
Good morning and Happy Thanksgiving,
My 75 Royal Monaco has decided that the right hand portion on the speedometer lights don't need to work any more. This happened once before. Earlier this year I pulled the unit out and checked all the bulbs. They all worked, then magically every bulb showed up for the party. Until yesterday morning. Only one bulb works in the clock, the radio never has lit up, now this. I seem to remember reading here somewhere the voltage limiter may be a culprit. Doesn't sound right, it seems that none of the bulbs would work if it was bad. I know the simplest answer is always best, but what does the limiter limit power to? Just the cluster? All of them? If its going bad does this problem happen? The FSM shows its attached to just about everything in the dash. But, the fuel and ammeter work just fine. I'm not sure I'm barking up the right tree here. Please advise and enjoy the turkey or ham or whatever! : )
Good Morning
The VR does not control the lights; only the gauges. My guess would be a loss of ground or a cracked circuit board/ open in the lighting circuit somewhere..... Radio light is probably kaput. It's internal to the radio and different that the dash bulbs.
You probably wanted an excuse to work on the Dodge anyway.....

It might take some doing, but peruse the FSM wiring schematic to see what feeds those bulbs themselves, which should have some connection to the i/panel light circuit, headlight switch, and panel dimmer function.

I suspect that the lights themselves are fed from a common printed circuit item, which they are twisted into. There might be some breaks in that item, which could be temperature sensitive? As for the radio lights, those would be a part of the radio itself, which gets back to the feed from the i/pnl dimmer mechanism. Similar with the hvac control panel, I suspect.

Please keep us posted.

Just some thoughts,