Primary and Secondary Air Pressure Gauges
Warning: If air pressure falls below minimum pressure, the braking ability of the vehicle will be limited. Slow the vehicle down and bring it to a gradual stop. Do not attempt to move the vehicle until air pressure has risen above the minimum level. Moving a vehicle without adequate braking power could cause an accident resulting in property damage, personal injury, or death.
Air pressure gauges, as shown in Fig., register the pressure in the primary and secondary air systems. The gauges are labeled for the A or B reservoir. Normal pressure with the engine running is 100 to 120 psi (689 to 827 kPa) in both systems.
Fig. 1, Air Pressure Gauge (reservoir A shown)
A low-air-pressure warning light and audible alert, connected to both the primary and secondary systems, activate when air pressure in either system drops below approximately 70 psi (483 kPa).
When the engine is started, the warning light and audible warning remain on until air pressure in both systems exceeds minimum pressure.