Refrigerant Pressure Switch Description

WARNING: This page is about a different car, the 2002 Mazda 626. However, it is still accessible from the selected car via links, so may be relevant.

The refrigerant pressure switch (HI) is installed in the cooler pipe No. 3.
The refrigerant pressure switch (LO) is installed on the accumulator tank.
If the pressure is abnormal, the refrigerant pressure switches cut the A/C signal sent from the climate control unit to the PCM, thereby stopping the A/C compressor.
The refrigerant pressure switches are used to respond to both abnormally high and abnormally low-pressure.

Fig 1: Refrigerant Pressure Switch Range Of Operation Specifications
Courtesy of MAZDA MOTORS CORP.