The numbers below refer to the step numbers on the diagnostic table.
Placing the mode switch in any position other than OFF, 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.
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 | Yes | No |
---|---|---|---|
Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views DEFINITION: The 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 HVAC Diagnostic System Check? | Go to Step 2 | |
Does the scan tool indicate that the ECT Sensor parameter is below 121°C (250°F)? | Go to Step 3 | Go to Engine Overheating in Engine Cooling | |
Important: For A/C compressor operation, ambient air temperature must be above 3°C (38°F).
Does the A/C compressor operate? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 4 | |
4 |
Does the system pass the A/C System Performance Test? | Go to Step 5 | Go to Leak Testing in Heating, Ventilation and Air Conditioning |
5 |
Are the 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 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 compressor clutch 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 |
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 in Wiring Systems. Did you find and correct the condition? | Go to Step 34 | Go to Step 17 |
16 | Test the low reference circuit of the A/C refrigerant pressure sensor for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. 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 in Wiring Systems. Did you find and correct the condition? | Go to Step 34 | Go to Step 27 |
18 | Test the control circuit of the A/C compressor clutch relay for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 34 | Go to Step 28 |
19 | Test the control circuit of the A/C compressor clutch relay for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. 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 in Wiring Systems. 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 in Wiring Systems. Did you find and correct the condition? | Go to Step 34 | Go to Step 26 |
22 | Repair the switch side voltage supply circuit of the A/C compressor clutch relay. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 34 | -- |
23 | Repair the coil side voltage supply circuit of the A/C compressor clutch relay. Refer to Wiring Repairs in Wiring Systems. 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 in Wiring Systems. 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 in Wiring Systems. 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 in Wiring Systems. 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 in Wiring Systems. 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 powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. 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 in Heating, Ventilation and Air Conditioning. Did you complete the replacement? | Go to Step 34 | -- |
30 | Replace the A/C compressor clutch relay. Refer to Compressor Relay Replacement in Heating, Ventilation and Air Conditioning. Did you complete the replacement? | Go to Step 34 | -- |
31 | Replace the A/C compressor clutch coil. Refer to Air Conditioning Clutch Coil Removal and Air Conditioning Clutch Coil Installation in Heating, Ventilation and Air Conditioning. Did you complete the replacement? | Go to Step 34 | -- |
32 |
Important: Perform the recalibration procedure for the HVAC control module. Replace the HVAC control module. Refer to HVAC Control Module Replacement . Did you complete the replacement? | Go to Step 34 | -- |
33 |
Important: Perform the programming procedure for the PCM. Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls. 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 |