I have an Allegro Bus, year 2000, 38 foot diesel pusher. My air pressure gauge will drop down to zero and then fluctuate between zero and 130 psi. While the gauge is going through this gyration, the air brake warning buzzer is on. Then, after a minute or so, the gauge will settle at the appropriate air pressure of 130 psi or even with the second gauge (which works perfect). I don't loose any of my air brakes, but it's a nuisances having this gauge perform in this manner (it doesn't do it all the time, just occasionally. Does anyone know the cause of this problem?