Q: Do the compressor supposed to always be turning if it is not turned on

If the A/C switch in the passenger compartment is turned off, any air delivered by the in-dash blower should simply be the same temperature as the passenger compartment, that is not chilled. If you have the A/C switch off and yet cold air is being delivered, that means there is an electrical problem that is causing the system to remain on when it is supposed to be off.

If you are looking at the pulley side of the physical compressor on the vehicle, the external pulley will ALWAYS be turning when the engine is running and so you might mistakenly think the A/C is on when in fact all that is turning is the pulley. When you turn the A/C system "on", a clutch behind the pulley mates the pulley to the compressor itself and it is ONLY at that point that the compressor turns and begins the vapor-compression cycle that creates cooled air in the passenger compartment. If you look at the center of the pulley, when the a/c is off, the central portion of the pulley should be stationary. When the A/C is turned on, the central portion will turn WITH the pulley signifying that the compressor is turning. If you want to have your vehicle’s A/C system checked out and evaluated, please request a comprehensive vehicle a/c system diagnostic. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.