A/C Compressor Control

When air conditioning (A/C) is selected ('ECON' off) the automatic temperature control (ATC) module maintains the evaporator at an operating temperature that varies with the cabin cooling requirements. If the requirement for cooled air decreases, the automatic temperature control (ATC) module raises the evaporator operating temperature by reducing the flow of refrigerant provided by the air conditioning (A/C) compressor.

If the requirement for cooled air increases, the automatic temperature control (ATC) module lowers the evaporator operating temperature by increasing the flow of refrigerant provided by the air conditioning (A/C) compressor.

When economy mode is selected by pressing the 'ECON' TSD soft button, the compressor current signal supplied by the automatic temperature control (ATC) module holds the air conditioning (A/C) compressor solenoid valve in the minimum flow position, effectively switching off the air conditioning (A/C) function.

The automatic temperature control (ATC) module incorporates limits for the operating pressure of the refrigerant system. When the system approaches the high pressure limit the compressor current signal is progressively reduced until the system pressure decreases. When the system pressure falls below the low pressure limit the compressor current signal is held at its lowest setting so that the air conditioning (A/C) compressor is maintained at its minimum stroke. This avoids depletion of the lubricant from the air conditioning (A/C) compressor.