Operation
The air conditioning system uses a compressor with variable displacement.
This compressor is referred to as the V-5 type compressor. The V-5 compressor
meets A/C requirements without cycling. The A/C compressor operation is
controlled by the Powertrain Control Module (PCM) for the following reasons:
| • | Improved idle quality during compressor clutch engagement. |
| • | Improved wide open throttle performance (WOT). |
| • | Protects the A/C compressor from operation with incorrect refrigerant
pressures. |
The A/C clutch electrical system consists of the following components:
| • | The A/C control head and/or the A/C programmer. |
| • | The A/C refrigerant pressure sensor. |
| • | The A/C compressor clutch. |
| • | The A/C compressor clutch relay. |
When an A/C mode is selected at the A/C control head, the A/C programmer
provides a 12 volt signal to the A/C request circuit. The PCM monitors
the A/C request circuit and controls the A/C compressor relay based on
the A/C request signal. This allows the PCM to increase the engine idle
speed just prior to A/C clutch engagement for better idle quality. In addition,
the PCM will command the cooling fans ON during A/C operation. The PCM
also monitors the A/C refrigerant pressure sensor circuit. If the A/C refrigerant
pressure is too high or low, the PCM will disable the A/C compressor relay.
The PCM will enable the A/C compressor clutch whenever the engine is
running and the A/C has been requested unless one or more of the following
conditions are present:
| • | Throttle angle is greater than 96%. |
| • | A/C head pressure is greater than 440 psi (4.6 volts)
or less than 33 psi (0.3 volt) as determined by the A/C refrigerant
pressure sensor. |
| • | Ignition voltage is less than 10 volts. |
| • | Engine speed is greater than 4400 RPM for any amount of time. |
| • | Engine speed is greater than 4392 RPM for less than 1 seconds. |
| • | ECT is greater than 124°C (255°F). |
| • | IAT is less than 5°C (41°F). |
Any of the conditions described above will inhibit A/C compressor relay
operation.
Diagnosis
DTC P0530, P0560, P1639, or P1641 can affect A/C operation. Refer to
Diagnostic Trouble Code (DTC) List
or
Diagnostic Trouble Code (DTC) List
if any DTCs are set.
The PCM Controlled Air Conditioning Diagnosis table should be used for
diagnosing the electrical portion of the A/C compressor clutch circuit if
a DTC is not set. To diagnose the refrigerant portion of the HVAC system,
refer to Refrigerant System Checks
in the Heater, Ventilation, and Air Conditioning (HVAC) System-Manual.
A scan tool will be used in diagnosing the system. The scan tool has the
ability to display the A/C request and refrigerant pressure inputs to the
PCM. The scan tool can display when the PCM has commanded the A/C clutch
ON. The scan tool also has the ability to override the A/C request signal
and energize the A/C control relay.
