A/C Pressure Switch

The A/C cycling switch is mounted on a Schrader valve-type fitting on the top of the suction accumulator/drier.
- A valve depressor, located inside the threaded end of the A/C cycling switch, presses in on the Schrader valve stem.
- This allows the suction pressure inside the suction accumulator/drier to control the operation of the A/C cycling switch.
- The electrical switch contacts open when the suction pressure drops to 152-193 kPa (22 to 28 psi).
- The contacts close when the suction pressure rises to 276-324 kPa (40-47 psi).
- Ambient temperature below approximately 7-10°C (45-50°F), during cold weather seasons, prevents the A/C cycling switch contacts from closing.
- This is due to the pressure/temperature relationship of the refrigerant and the requirement of the system pressure to reach 276-324 kPa (40-47 psi) to close the A/C cycling switch contacts.
- When the A/C cycling switch contacts close, the signal to energize the A/C clutch is sent to the powertrain control module.
- The powertrain control module then supplies the voltage to energize the A/C clutch for A/C compressor operation.
- When the A/C cycling switch contacts open, the powertrain control module opens the A/C clutch electrical circuit to de-energize the A/C clutch. A/C compressor operation stops.
- The A/C cycling switch will control the A/C evaporator core pressure at a point where the plate/fin surface temperature will be maintained slightly above freezing.
- This prevents icing of the A/C evaporator core and blockage of airflow.