revnexis

If there’s no air at the parking brake valve, the problem is likely upstream. The dash valve is usually fed from the primary air system through the parking protection valve, so check that the primary tank is building air and the PPV is opening. I’d also trace the supply line back for a missed, capped, or plugged line from reassembly.

On an ’84 R-Model this is almost always a ground issue or voltage back-feeding. All red lights with the circuit chaser usually indicate a poor cab, frame, or rear light ground, often from corrosion. The turn signal flashing red and green is a classic weak ground at the rear lamp housings or a bad cab-to-frame ground strap. I’d start by checking and cleaning the cab-to-frame ground, battery/frame grounds, and rear light grounds before chasing switches or wiring.