The Refrigerant Cycle
For information regarding base refrigerant operation within the HVAC system . The diagram below shows the refrigerant system state in each component on this vehicle.
The following statements apply to this refrigerant system:
- The PCM controls the A/C clutch relay.
- The evaporator temperature sensor monitors the temperature of the evaporator core and sends a signal to the PCM. If the temperature of the evaporator core is low enough to cause the condensed water vapor to freeze, the A/C clutch is disengaged by the PCM.
- The line pressure is monitored so that A/C compressor operation is interrupted if the system pressure becomes too high or too low.
- The A/C compressor relief valve opens and vents refrigerant to relieve unusually high system pressure.
TXV Type Refrigerant System State and Flow - GTDI
| Item | Description |
|---|---|
| 1 | High pressure liquid |
| 2 | Low pressure liquid |
| 3 | High pressure vapor |
| 4 | Low pressure vapor |
TXV Type Refrigerant System State and Flow - Ti-VCT
| Item | Description |
|---|---|
| 1 | High pressure liquid |
| 2 | Low pressure liquid |
| 3 | High pressure vapor |
| 4 | Low pressure vapor |
Compressor Anti-Slugging Strategy (CASS)
Liquid refrigerant may accumulate in the A/C compressor under certain conditions. To reduce damage to the A/C compressor, Compressor Anti-Slugging Strategy (CASS) is utilized.
CASS is initiated only under specific conditions:
- Ignition is off for more than 8 hours
- Ambient temperature is above -4°C (25°F)
- Battery voltage is above 8.5 volts during engine cranking
When these conditions are present, the PCM activates the A/C control relay prior to cranking of the engine. The A/C control relay engages the A/C compressor for approximately 4-15 A/C compressor revolutions or a maximum of 2 seconds (depending upon vehicle application), allowing the liquid refrigerant to be pushed from the A/C compressor. CASS is initiated by the PCM regardless of the HVAC system settings.