A/C Cyclic Switch

The A/C cyclic switch (19E561) is mounted on a Schrader valve fitting on the top of the suction accumulator/drier (19C836) assembly (refer to Suction/Accumulator/Drier illustration).

• A valve depressor, located inside the threaded end of the A/C cyclic switch , presses in on the Schrader valve stem as the A/C cyclic switch is mounted.
• This allows the suction pressure inside the suction accumulator/drier canister to control A/C cyclic switch operation.
• The electrical switch contacts will open when the suction pressure drops to 152-193 kPa (22-28 psi). The contacts will close when the suction pressure increases to 276-324 kPa (40-47 psi).
• Ambient temperature below approximately 45-50°F (7-10°C) will prevent the A/C cyclic pressure switch contacts from closing.
• The A/C cyclic switch contacts control the electrical circuit to the A/C compressor clutch field coil (2987) .
• When the A/C cyclic switch contacts close, the signal to energize the A/C clutch (2884) is sent to the Constant Control Relay Module (CCRM).
• The CCRM then supplies the voltage to energize the A/C clutch for A/C compressor (19703) operation. When the A/C cyclic switch contacts open, the CCRM opens the A/C clutch electrical circuit to de-energize the A/C clutch and A/C compressor operation stops.
• The A/C cyclic switch , when functioning properly, will control the A/C evaporator core pressure at a point where the plate/fin surface temperature will be maintained slightly above freezing which prevents A/C evaporator core (19860) icing and the blockage of airflow.