My 1973 F-100 instrument gauges are fluctuating slowly.Would this be the instrument cluster regulator or the backing plate?Should I just replace both of them while I have dash apart?I notice my temperature reads higher and the oil pressure reads higher at the same time and then sometimes they read back to the lower side?Has anyone had this problem?

 

It sure sounds like the voltage regulator is going out. Slight chance it could be a dirty ground also (mount screw ground? I've forgotten). I'd clean ground points first and re-check... then replace the IVR.

 

I have the same issue on my 79 F100. The oil pressure gauge is up and then its down. The temperature gauge is up and then its down. Fuel Gauge works fine though. ALT Gauge may be a tad iffy. Guess its time to check all connections etc and maybe see about the IVR (where it is and what it looks like )

 

Haven't had a Ford truck that didn't do it, varies with voltage and gauges seem to work off each other a bit...Until the 90's when they started using preset oil pressure gauges that read just past half way if you have any oil pressure.