An HVAC pressure switch ensures proper operation and protects the system from damage. The switch monitors the pressure of the refrigerant in the system and, if the pressure falls below or rises above a certain level, the switch will shut off the system to prevent further damage.It is important to keep your AC pressure switch in good working condition to ensure the safe and efficient operation of your air conditioning system. AC high pressure switch replacement is necessary when you suspect that it needs to be replaced.