A/c switch

99 grand prix. controls are manual version, not automatic climate control. a/c works fine but compressor is engaged whether a/c button is pushed on or off. the only way i can disable a/c is too set fan speed to OFF. does not matter if control is set to vent, or feet. a/c runs with a/c switch set to on or off. this is not an issue of selector set to dash or defrost. i assume it is not a clutch gap issue since the compressor shuts off if i turn fan control to OFF.

Possibly the switch is shorted internally.