The refrigerant temperature at the evaporator 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 Sensor Resistance Table to review sensor resistance through the temperature ranges.
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 128°C (262°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).
DTC B3933 A/C evaporator temperature sensor circuit may also set to diagnose this circuit.
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 128°C (262°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 22 | ||||||
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 9 | Go to Step 8 | ||||||
8 |
Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 39 | Go to Step 9 | ||||||
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 25 | ||||||
11 |
Does the test lamp turn ON and OFF with each command? | Go to Step 27 | Go to Step 12 | ||||||
12 | Does the test lamp remain illuminated with each command? | Go to Step 19 | Go to Step 17 | ||||||
13 |
Does the test lamp illuminate? | Go to Step 14 | Go to Step 24 | ||||||
14 |
Does the A/C compressor clutch engage? | Go to Step 27 | Go to Step 20 | ||||||
15 | Test the ignition 1 voltage circuit of the HVAC control module for the following conditions:
Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 39 | Go to Step 16 | ||||||
16 | 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 39 | Go to Step 31 | ||||||
17 | 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 39 | Go to Step 32 | ||||||
18 | Test the A/C request signal circuit for the following conditions:
Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 39 | Go to Step 21 | ||||||
19 | 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 39 | Go to Step 32 | ||||||
20 | Test the supply voltage circuit at the A/C compressor clutch relay for the following conditions:
Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 39 | Go to Step 23 | ||||||
Is the resistance measured within the minimum/maximum resistance range for the temperature value indicated? | Go to Step 22 | Go to Step 29 | |||||||
22 | 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 39 | Go to Step 26 | ||||||
23 | 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 39 | Go to Step 28 | ||||||
24 | Repair the switch side voltage supply circuit of the relay. Refer to Wiring Repairs . Did you complete the repair? | Go to Step 39 | -- | ||||||
25 | Repair the coil side of the voltage supply circuit of the relay. Refer to Wiring Repairs . Did you complete the repair? | Go to Step 39 | -- | ||||||
26 | 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 39 | Go to Step 33 | ||||||
27 | 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 39 | Go to Step 35 | ||||||
28 | 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 39 | Go to Step 36 | ||||||
Test the evaporator temperature sensor circuits for the following conditions:
Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 39 | Go to Step 30 | |||||||
30 | Inspect for poor connections at the harness connector of the evaporator temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 39 | 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 39 | Go to Step 37 | |||||||
32 | Inspect for poor connections at the harness connector of the PCM/ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 39 | Go to Step 38 | ||||||
33 | 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 39 | -- | ||||||
34 | Replace the evaporator temperature sensor. Refer to Evaporator Temperature Sensor Replacement . Did you complete the replacement? | Go to Step 39 | -- | ||||||
35 | Replace the relay. Did you complete the replacement? | Go to Step 39 | -- | ||||||
36 | Replace the A/C compressor. Refer to Air Conditioning Compressor Replacement . Did you complete the replacement? | Go to Step 39 | -- | ||||||
37 | Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 39 | -- | ||||||
38 | Replace the PCM/ECM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | Go to Step 39 | -- | ||||||
39 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 4 |