The pressure cycling switch, detecting low refrigerant line pressure at 21-27 psi, turns the
A/C Compressor off and on again at 42 psi. If pressure exceeds 455-495 psi, the high-pressure cut-off switch near the compressor turns it off. To replace, disconnect the electrical connector and unscrew the switch from the Schrader valve. No need to discharge the A/C system. Lubricate the switch O-ring with clean refrigerant oil, screw the new switch until hand tight, then secure it. Reconnect the electrical connector.