Cutlass L4-138 2.3L VIN A FI HP (1990)
Control Module HVAC: Description and Operation
A/C Control Assembly
A/C CONTROL ASSEMBLY
Automatic and Manual Modes
The automatic A/C control assembly, uses short- travel, soft-touch buttons for selecting the mode, temperature and blower speeds manually, if
desired. In the automatic mode, the desired temperature is set by the driver and a microprocessor utilizes this information along with the two air
temperature sensor inputs to provide the desired comfort level. The driver can override the auto blower speed and mode selection, if desired. For
example, if a different mode is selected, the microprocessor will continue to moderate the blower speed and temperature.
System Self-tests
The microprocessor also provides for system self-tests which result in diagnostic codes being displayed.
Diagnostic Mode
Faults in the inside and outside temperature sensor circuits and temperature valve control circuit are identified when the control assembly is set to
the diagnostic mode. Diagnostic mode activation and fault code identification are described in Testing and Inspection.
Figure 2 System Response/Operation
Control Assembly Operation
Basic control assembly operation is shown in Figure 2. Full operational instructions, system checks and tests of the A/C control assembly are
located under Testing and Inspection.
