Home › CDL Practice Tests › Air Brakes Questions › Question 18
A driver notices the primary gauge falling while the secondary gauge stays normal. What does this most likely indicate?
- A.Both circuits have failed at the same time
- B.The gauges should be ignored until the trip ends
- C.A leak or failure isolated to the primary circuit
- D.The compressor governor needs more fuel
Correct answer
C. A leak or failure isolated to the primary circuit
Why
Because the circuits are separated by check valves, one side can lose pressure while the other holds. The correct response is to stop safely and find the leak rather than relying on the remaining circuit for the rest of the trip.
Manual topic: Air Brakes - Dual Air Brake Systems · From the Air Brakes practice bank (AB-018).