Test Description
The numbers below refer to the step numbers on the diagnostic table.
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Placing the fan switch in the ON position, along with placing the air temperature control switch in a cold setting, activates A/C operation. For the purpose of this and future steps where A/C operation is necessary, bi-level mode is used for consistent testing.
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The HVAC control module is inoperative when the module does not respond to any operator control requests to enable the A/C compressor. The blower motor may still operate independent of the A/C controls.
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 scan tool indicate that the ECT parameter is above the specified temperature? | 124°C (255°F) | Go to Engine Overheating | Go to Step 3 | |
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Important: Ambient air temperature (AAT) must be above 3°C (38°F).
Does the A/C compressor operate? | -- | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 4 | |
4 |
Are the pressure values within specifications for the ambient air temperature, and within 103 kPa (15 psi) of each other? | -- | Go to Step 5 | Go to Leak Testing |
5 |
Are the high side pressure values within 103 kPa (15 psi) of each other? | -- | Go to Step 6 | Go to Step 16 |
Is the HVAC control module inoperative? | -- | Go to Step 15 | Go to Step 7 | |
7 |
Does the scan tool indicate that the A/C Request Signal parameter is YES? | -- | Go to Step 8 | Go to Step 27 |
8 | With a scan tool, observe the A/C Relay Command status in the Powertrain Control Module (PCM) data list. Does the scan tool indicate that the A/C Relay Command status is ON? | -- | Go to Step 9 | Go to Step 28 |
9 | With a scan tool, command the A/C Relay ON and OFF. Does the A/C compressor clutch relay turn ON and OFF with each command? | -- | Go to Step 13 | Go to Step 10 |
10 |
Does the test lamp illuminate? | -- | Go to Step 11 | Go to Step 23 |
11 |
Does the test lamp turn ON and OFF with each command? | -- | Go to Step 25 | Go to Step 12 |
12 | Does the test lamp remain illuminated with each command? | -- | Go to Step 19 | Go to Step 18 |
13 |
Does the test lamp illuminate? | -- | Go to Step 14 | Go to Step 22 |
14 | Connect a 10-amp fused jumper wire between the switch side battery positive voltage circuit of the A/C compressor clutch relay and the A/C compressor clutch supply voltage circuit of the A/C compressor clutch. Does the A/C compressor clutch engage? | -- | Go to Step 25 | Go to Step 20 |
15 | Test the ignition 3 voltage circuit of the HVAC control module for a short to ground, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 34 | Go to Step 17 |
16 | Test the ground circuit of the A/C refrigerant pressure sensor for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 34 | Go to Step 24 |
17 | Test the ground circuit of the HVAC control module for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 34 | Go to Step 27 |
18 | Test the A/C compressor clutch relay control circuit of the A/C compressor clutch relay for an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 34 | Go to Step 28 |
19 | Test the A/C compressor clutch relay control circuit of the A/C compressor clutch relay for a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 34 | Go to Step 28 |
20 | Test the A/C compressor clutch supply voltage circuit at the A/C compressor clutch for a short to ground, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 34 | Go to Step 21 |
21 | Test the ground circuit of the A/C compressor clutch for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 34 | Go to Step 26 |
22 | Repair the switch side battery positive voltage circuit of the A/C compressor clutch relay. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 34 | -- |
23 | Repair the coil side battery positive voltage circuit of the A/C compressor clutch relay. Refer to Wiring Repairs . Did you complete the repair? | -- | Go to Step 34 | -- |
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 34 | Go to Step 29 |
25 | Inspect for poor connections at the A/C compressor clutch relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 34 | Go to Step 30 |
26 | Inspect for poor connections at the harness connector of the A/C compressor clutch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 34 | Go to Step 31 |
27 | 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 34 | Go to Step 32 |
28 | 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 34 | Go to Step 33 |
29 | 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 34 | -- |
30 | Replace the A/C compressor clutch relay. Refer to Compressor Relay Replacement . Did you complete the replacement? | -- | Go to Step 34 | -- |
31 | Replace the A/C compressor clutch. Refer to Compressor Clutch Assembly Replacement . Did you complete the replacement? | -- | Go to Step 34 | -- |
32 | Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 34 | -- |
33 | Replace the PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 34 | -- |
34 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 4 |
