Primary and 2nd air gauges

[Chamberpains]

I'm not familiar with the prostar circuits. But anytime a gauge spikes off at 6 o'clock it is an indication that the gauge itself either lost signal or the circuit lost power. I would start by checking fuses for your instrument panel and if it has a separate circuit for your air gauges. It can also be an indication that the gauge section of your instrument cluster has failed. But start with fuses, wiring and sensors for your air guages first.

Rawze and other guys have stated that the spades on the fuses and breakers in the prostars look fine but get a corrosion or patina on them that doesn't allow proper voltage through. Many of them have replaced all their fuses and fixed a lot of different problems by doing this.