When standing in front of the vehicle, the compressor is the top-right most pulley. The pulley will always spin, but the clutch that is in front of the pulley will engage and spin when the compressor is on, and be stationary when the compressor is off.

On my vehicle simply turning on the fan, with the A/C off, engages the clutch. It sounds like at least 2 other people are reporting this happens with the A/C button.

Kurt