Instrument cluster voltage regulator, on a 1970 Plymouth Valiant, 340 Duster

only the temp and fuel are powered thru the limiter the oil pressure is not .


No, only the amp gauge is not associated with the limiter. The other three are. The fuel gauge has a 3rd post which is the 5V output and feeds to the oil/ temp gauges. See Red's post above^^

In fact you can see it in the photo posted, marked 5V

inkedimg_0034_li-jpg.jpg