[C10 - C90 Bill]

If the truck has an air leak, most likely when you jump in the truck, the Air Pressure will be down or out. When down about 30 Lbs from full, or a little lower, the Buzzer will come on. If you somehow have full pressure when you first get in the truck, keep pumping the Air Brakes till the Buzzer comes on. Hopefully the Air Pressure Gauge works. It should be mechanical. If the Gauge works, but the Buzzer doesn't for some reason, keep a consistent eye on the Gauge while driving it.