[77newell]

On my 93 coach the ppv is located on the bulkhead in front of the rear axle near a pair of quarter turn ball valves and the pressue switch that triggers the the low air pressure light. Unless someone got under the coach and shut the ball valves the ppv is the only restrictor of air to the gauge. Since the brakes are pressuring the supply tank itself is pressurizing. One final check would be to check the pressure gauge at the rear six pack. If it is low then the ppv is likely stuck closed, it seems to happen at the weirdest time.

Basically, the dash gauge is fed from a distributor block adjacent to the front six pack. The supply to that block comes from one of the two ball valves I mentioned above, the supply to the rear of the coach comes through the other ball valve. A T after the ppv supplies the two ball valves. The ppv is supplied by the rear air tank known as the service tank. This is the arrangement on my 93 coach. The ppv is quite cheap, changing isn't hard but will cost you some skin.