The air compressor should be inspected only when
- the engine is off. ✓
- the engine is idling.
- the vehicle is parked on a level surface.
- the parking brakes are released.
Answer: A. the engine is off.
The air compressor should be inspected only when the engine is off.
Why this is the answer
The air brake handbook says air compressors must always be inspected with the engine stopped. It also explains that moving parts in the engine compartment are a hazard, so inspections are done with the engine stopped. Checking compressor mounting, pulleys and belt condition or tension is therefore a stopped-engine task, not something to do while the engine is idling. That is why the engine-off choice is the correct condition for inspecting the compressor.
Why the other answers are wrong
- B. the engine is idling. — An idling engine is still running, and the handbook requires the engine to be stopped for an air compressor inspection because moving engine parts are hazardous.
- C. the vehicle is parked on a level surface. — A level surface is a general air brake inspection precaution to reduce rolling, but it is not the condition that specifically governs inspecting the air compressor.
- D. the parking brakes are released. — Having the parking brakes released is required for some air brake inspection steps, not for the air compressor check, which is about the engine being stopped.
Remember it
Think "compressor check, engine off" — the belt and pulley are checked with everything stopped.