The refrigerant temperature at the temperature sensor in the thermal expansion valve (TXV) controls cycling of the compressor clutch to prevent freezing of the evaporator core. The compressor is disabled when the temperature goes below 3°C (37°F) and vehicle speed is greater than 8 km/h (5 mph). The compressor is enabled when the temperature exceeds 4°C (40°F). The minimum cycling time OFF is 4 seconds. Refer to Air Temperature Description and Operation for a voltage temperature value table of the evaporator temperature sensor.
The numbers below refer to the step numbers on the diagnostic table.
The air conditioning (A/C) compressor relay output is disabled if the engine coolant temperature is above 96°C (205°F).
Place the mode switch in any position except OFF, and place the air temperature control switch in a cold setting. Use the bi-level mode for consistent testing of the A/C system operation.
The HVAC control module is inoperative if the module does not respond to any operator control requests.
The compressor is disabled when the evaporator temperature goes below 3°C (38°F).
Check the connection by removing and securely reinstalling before replacement of the HVAC control is considered.
Step | Action | 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 if 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 96°C (205°F)? | Go to Engine Overheating | Go to Step 3 | |||||||
Important: For A/C compressor operation, the evaporator air temperature must be above 3°C (38°F).
Does the A/C compressor clutch operate? | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 4 | |||||||
4 |
Are the low and high side pressure values within the allowable limits for the recorded 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 24 | ||||||
Is the HVAC control module inoperative? | Go to Step 16 | Go to Step 7 | |||||||
7 |
Does the scan tool indicate that the A/C Request Signal parameter is Yes? | Go to Step 10 | Go to Step 8 | ||||||
8 |
Does the scan tool indicate that the A/C Request parameter is ON? | Go to Step 9 | Go to Step 18 | ||||||
9 |
Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 43 | Go to Step 10 | ||||||
10 | 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 14 | Go to Step 11 | ||||||
11 |
Does the test lamp illuminate? | Go to Step 12 | Go to Step 27 | ||||||
12 |
Does the test lamp turn ON and OFF with each command? | Go to Step 29 | Go to Step 13 | ||||||
13 | Does the test lamp remain illuminated with each command? | Go to Step 21 | Go to Step 19 | ||||||
14 |
Does the test lamp illuminate? | Go to Step 15 | Go to Step 26 | ||||||
15 |
Does the A/C compressor clutch engage? | Go to Step 29 | Go to Step 22 | ||||||
16 | Test the ignition 3 voltage circuit of the HVAC control module for the following:
Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 43 | Go to Step 17 | ||||||
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 43 | Go to Step 34 | ||||||
18 |
Does the value measure near battery voltage? | Go to Step 31 | Go to Step 20 | ||||||
19 | Test the 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 43 | Go to Step 35 | ||||||
20 | Test the A/C request signal circuit for the following:
Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 43 | Go to Step 23 | ||||||
21 | Test the 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 43 | Go to Step 35 | ||||||
22 | Test the supply voltage circuit at the A/C compressor clutch relay for the following:
Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 43 | Go to Step 25 | ||||||
View the evaporator voltage in the BCM scan tool data list under A/C sensor. Refer to Air Temperature Description and Operation for the evaporator sensor temperature to voltage conversion chart. Is the Evaporator Voltage parameter greater than the voltage range of 2.45-2.55 V which equals a temperature range of 36-38°F (2.22-3.33°C)? | Go to Step 32 | Go to Step 24 | |||||||
24 | Test the ground circuit of the A/C refrigerant pressure sensor 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 43 | Go to Step 28 | ||||||
25 | 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 43 | Go to Step 30 | ||||||
26 | Repair the switch side voltage supply circuit of the relay. Refer to Wiring Repairs . Did you complete the repair? | Go to Step 43 | -- | ||||||
27 | Repair the coil side of the voltage supply circuit of the relay. Refer to Wiring Repairs . Did you complete the repair? | Go to Step 43 | -- | ||||||
28 | 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 43 | Go to Step 36 | ||||||
29 | Inspect for poor connections at the relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 43 | Go to Step 38 | ||||||
30 | 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 43 | Go to Step 39 | ||||||
31 | Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 43 | Go to Step 41 | ||||||
32 | Test the evaporator temperature sensor circuits for the following:
Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 43 | Go to Step 33 | ||||||
33 | Inspect for poor connections at the harness connector of the evaporator low temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 43 | Go to Step 34 | ||||||
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 43 | Go to Step 37 | |||||||
35 | Inspect for poor connections at the harness connector of the ECM/PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 43 | Go to Step 42 | ||||||
36 | 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 43 | -- | ||||||
37 | Replace the evaporator low temperature sensor. Refer to Air Conditioning (A/C) Refrigerant Low Temperature Sensor Replacement . Did you complete the replacement? | Go to Step 43 | -- | ||||||
38 | Replace the relay. Did you complete the replacement? | Go to Step 43 | -- | ||||||
39 | Replace the A/C compressor clutch. Refer to Compressor Clutch Assembly Replacement . Did you complete the replacement? | Go to Step 43 | -- | ||||||
40 | Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 43 | -- | ||||||
41 | Replace the BCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 43 | -- | ||||||
42 | Replace the ECM/PCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 43 | -- | ||||||
43 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 4 |