Home › CDL Practice Tests › Air Brakes Questions › Question 79
During the applied test, pressure drops quickly at first and then steadies. How should that initial drop be treated?
- A.It counts as an instant failure in all cases
- B.It means the test must be done with the engine racing
- C.It proves the slack adjusters are broken
- D.It is the normal stabilization as chambers fill and pressure equalizes; the one-minute timing starts after it settles
Correct answer
D. It is the normal stabilization as chambers fill and pressure equalizes; the one-minute timing starts after it settles
Why
Filling the chambers consumes air and the gauge always steps down once before steadying. Judging the system on that first step would fail healthy trucks, so the standard allows stabilization before timing begins.
Manual topic: Air Brakes - Air Leakage and Brake Tests · From the Air Brakes practice bank (AB-079).