HVAC System
CIRCUIT DESCRIPTIONWhen the A/C button is pressed ON, battery voltage is supplied to terminal 2 of the A/C compressor refrigerant pressure switch. The A/C pressure switch is closed when the pressure in the refrigerant line is approximately 180 kPa (36 psi). With the pressure switch closed, battery voltage is supplied to terminal 58 connector C2 of the Engine Control Module (ECM). After receiving the A/C request input, the ECM grounds the A/C compressor relay coil which energizes the relay closing the relay contacts. With the relay contacts closed, the circuit is completed allowing battery voltage to be applied to the A/C compressor clutch coil. The A/C compressor clutch coil energizes and the compressor clutch will now engage.
The heater and A/C control monitors the ECM when it energizes or de-energizes the A/C compressor relay coil. The heater and A/C control monitors the circuit at terminal 9 connector C1. This circuit is in parallel with the control side of the relay coil.
CONDITIONS FOR SETTING THE DTC
^ The heater and A/C control monitors the request circuit for a short to ground every 40 ms on a continuous basis.
^ The request circuit stays at or near zero volts.
ACTION TAKEN WHEN THE DTC SETS
^ The heater and A/C control stores a DTC 36 in memory.
^ The heater and A/C control internally disables the output.
CONDITIONS FOR CLEARING THE DTC
^ The conditions for the fault are no longer present.
^ Using a scan tool.
^ A history DTC will clear after 20 consecutive ignition cycles if the condition for the fault is no longer present.
DIAGNOSTIC AIDS
If condition not present, refer to Testing for Intermittent and Poor Connections in Diagrams.
TEST DESCRIPTION
Steps 1-5:
Steps 1-5:
The number(s) below refer to the step number(s) on the diagnostic table.
2. Tests for voltage to the ECM and determines if the circuit is complete.