Diagnostic Aids
| • | The air conditioning (A/C) compressor is protected from overheating by the compressor temperature switch, which is mounted at the rear of the A/C compressor. The switch is wired internally to the compressor and is not serviceable. The switch opens and disengages the compressor clutch when temperatures reach 135°C (275°F). The switch closes when the compressor temperature cools to 120°C (248°F). |
| • | A/C compressor clutch will not engage under the following conditions: |
| - | The A/C high side line pressure is over 2,413 kPa (350 psi). |
| - | The A/C low side line pressure is under 151 kPa (22 psi). |
| - | Throttle angle is at 100 percent. |
| - | Engine speed is more than 5,500 RPM. |
| - | Engine coolant temperature (ECT) is more than 123°C (253°F). |
| - | Ambient air temperature is less than 1°C (35°F). |
| - | Engine is idling at a low unstable RPM. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The A/C compressor output is disabled if the engine is idling at a low unstable RPM.
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The A/C compressor relay output is disabled if engine coolant temperature is above 123°C (253°F). The engine coolant indicator will illuminate at this temperature.
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This step ensures that the HVAC control module is receiving an input from the A/C switch.
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These actions will enable the A/C compressor to operate.
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This test ensures that there is sufficient refrigerant in the A/C system. The specific values come from the A/C System Performance Test in Heating, Ventilation and Air Conditioning.
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The A/C low pressure switch parameter is out of range when the HVAC control module interprets the signal being below 151 kPa (22 psi) or above 275 kPa (40 psi).
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This action will simulate a closed switch condition. If the Pressure Cycle Switch parameter reads Low Pressure than there is a circuit condition or a condition with the HVAC control module.
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The A/C compressor relay output from the powertrain control module (PCM) is disabled if the A/C high side system pressure is interpreted to be higher than 2,413 kPa (350 psi).
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views DEFINITION: The air conditioning (A/C) compressor clutch will not engage when an A/C request has been made and a Powertrain DTC has not been set. | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
Does the engine idle at a steady RPM? | -- | Go to Step 3 | Go to Rough, Unstable, or Incorrect Idle and Stalling for the 4.2L engine | |
Is the engine coolant temperature indicator illuminated? | -- | Go to Step 4 | ||
Does the A/C Switch parameter change states when the A/C request switch is pressed? | -- | Go to Step 5 | Go to Step 26 | |
|
Important: For A/C compressor operation, the ambient air temperature display must be above 1°C (35°F). Refer to Ambient Air Temperature Display Updating .
Does the A/C compressor clutch engage? | -- | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 6 | |
Are the low and the high side pressure values within the allowable limits for the recorded ambient air temperature? Are the pressure values within 103 kPa (15 psi) of each other? | Above 16°C (60°F) 345 kPa (50 psi) Above 24°C (75°F) 483 kPa (70 psi) Above 33°C (90°F) 690 kPa (100 psi) | Go to Step 7 | Go to Leak Testing | |
7 |
Does the A/C Permission parameter display Granted? | -- | Go to Step 14 | Go to Step 8 |
Does the Pressure Cycle Switch parameter display Normal? | -- | Go to Step 12 | Go to Step 9 | |
Does the Pressure Cycle Switch parameter display Normal? | -- | Go to Step 23 | Go to Step 10 | |
10 | Test the signal circuit of the A/C low pressure switch for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 11 |
11 | Test the ground circuit of the A/C low pressure switch for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 26 |
With a scan tool, observe the A/C High Side Pressure parameter in the Powertrain data list. Is the parameter less than the specified value? | 2,413 kPa (350 psi) | Go to Step 26 | Go to Step 13 | |
13 |
Are the high side pressure values within 103 kPa (15 psi) of each other? | -- | Go to Step 24 | |
14 | With a scan tool, observe the A/C Compressor Feedback parameter in the Heating and Air Conditioning data list. Does the A/C Compressor Feedback parameter display On? | -- | Go to Step 15 | Go to Step 16 |
15 | Test the ground circuit of the A/C compressor clutch for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 25 |
16 |
Does the relay turn ON and OFF with each command? | -- | Go to Step 17 | Go to Step 19 |
17 |
Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 18 |
18 | Test the supply voltage circuit of the A/C compressor clutch for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 22 |
19 |
Does the test lamp illuminate? | -- | Go to Step 20 | Go to Step 28 |
20 |
Does the test lamp illuminate? | -- | Go to Step 22 | Go to Step 21 |
21 |
Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 27 |
22 |
Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 29 |
23 | Inspect for poor connections at the harness connector of the A/C low pressure switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 30 |
24 | Inspect for poor connections at the harness connector of the A/C refrigerant pressure sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 31 |
25 | Inspect for poor connections at the harness connector of the A/C compressor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 32 |
26 | Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 33 |
27 | Inspect for poor connections at the harness connector of the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 35 | Go to Step 34 |
28 | Repair the ignition 3 voltage circuit of the A/C compressor clutch relay. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 35 | -- |
29 | Replace the A/C compressor clutch relay. Did you complete the replacement? | -- | Go to Step 35 | -- |
30 | Replace the A/C low pressure switch. Refer to Air Conditioning Cycling Switch Replacement . Did you complete the replacement? | -- | Go to Step 35 | -- |
31 | Replace the A/C refrigerant pressure sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement . Did you complete the replacement? | -- | Go to Step 35 | -- |
32 | Replace the A/C compressor. Refer to Air Conditioning Compressor Replacement . Did you complete the replacement? | -- | Go to Step 35 | -- |
33 | Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 35 | -- |
34 | Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 35 | -- |
35 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 5 |
