The A/C Compressor Cut-Out Switches are located on the hard line from the condenser to the evaporator core, at the firewall. They sense low refrigerant line pressure, turn off the A/C system, and turn it back on for higher pressure. The system will be deactivated by the pressure cut-off on the high-pressure side if the system pressure rises excessively. A technician should remove refrigerant from the air conditioning system. The electrical connectors from the A/C Compressor Cut-Out Switches should be disconnected and unscrewed. Apply clean refrigerant oil of the correct type to the O-rings of the new switches. Install the new switches by screwing them in until hand tight and securing them. Reattach the connectors, then have the system evacuated, recharged and leak tested by the same shop that discharged it.