A/C compressors are difficult to work with because of the refrigerant stored inside. When a compressor clutch does not disengage, it will cause the refrigerant to build up and freeze the line. To disengage the clutch, a switch must be replaced.
The Low-Pressure Switch
The low-pressure switch tells the car that the clutch needs to engage and disengage and will shut off the A/C compressor. When the switch goes bad, it will no longer be able to measure pressure and will leave the clutch engaged the entire time. This switch is located on the metal canister next to the compressor. It is screwed into the refrigerant canister and has two wires extending from it toward the wiring harness.