Thermal switches are used on both the low and high side of AC systems. A Thermal switch may be connected in series with the compressor clutch.
A/C compressor cycling control .
A thermostatic switch de-energizes the clutch and stops the compressor to keep the evaporator from freezing up. When the temperature of the evaporator approaches the freezing point (or the low setting of the switch), the thermostatic switch opens the circuit and disengages the compressor clutch. The compressor remains inoperative until the evaporator temperature rises to the preset temperature, at which time the switch closes and compressor operation resumes.
A/C Compressor temperature control.
A thermal limit switch may be mounted on or near the compressor and is used to stop compressor operation before the temperature of the compressor reaches a point of damage.