Cluster regulator varying output

The bottom line is that the unit is operating correctly.
The IVR has a bi metal spring set up that flexes creating contact, then it heats up breaking contact then cools off creating a contact then Heats up .....

This is how it works from the factory. Simple, effective for the time.
MoPar Muscle was back when showed you how to create your own solid state from Radio Shack parts. I did mine this way and it has worked for over 20 years now.

I just don't get why the car is a 12 volt system and the gauges are 5 volt. But that's the way it is.