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 assembly is inoperative when the module does not respond to any operator control requests.
The evaporator temperature sensor is replaced as part of the evaporator core.
Step | Action | Yes | No |
---|---|---|---|
Schematic Reference: HVAC Schematics 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 review the HVAC operation and perform the necessary inspections? | Go to Step 2 | |
Is the engine coolant temperature indicator illuminated? | Go to Engine Coolant Temperature Indicator Always On in Engine Cooling | Go to Step 3 | |
Important: For A/C compressor operation, ambient air temperature must be above 3°C (38°F).
Does the A/C compressor clutch engage? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | 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 in Heating, Ventilation and Air Conditioning |
5 |
Are the pressure values within specifications for the ambient air temperature, and 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 19 | Go to Step 7 | |
7 |
Does the scan tool indicate that the A/C request signal parameter is YES? | Go to Step 13 | Go to Step 8 |
8 | Does the A/C request indicator illuminate? | Go to Step 9 | Go to Step 33 |
9 |
Did you find and correct the condition? | Go to Step 41 | Go to Step 10 |
10 |
Does the resistance measure near the values specified in the sensor resistance table? | Go to Step 11 | Go to Step 31 |
11 | Test the evaporator temperature signal circuit 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 41 | Go to Step 12 |
12 | Test the low reference circuit 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 41 | Go to Step 28 |
13 | 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 17 | Go to Step 14 |
14 |
Does the test lamp illuminate? | Go to Step 15 | Go to Step 27 |
15 |
Does the test lamp turn ON and OFF with each command? | Go to Step 30 | Go to Step 16 |
16 | Does the test lamp remain illuminated with each command? | Go to Step 22 | Go to Step 21 |
17 |
Does the test lamp illuminate? | Go to Step 18 | Go to Step 26 |
18 |
Does the A/C compressor clutch engage? | Go to Step 30 | Go to Step 23 |
19 | 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 41 | Go to Step 20 |
20 | 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 41 | Go to Step 33 |
21 | 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 41 | Go to Step 34 |
22 | 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 41 | Go to Step 34 |
23 | 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 41 | Go to Step 25 |
24 | Test the ground circuit of the A/C 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 41 | Go to Step 29 |
25 | 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 41 | Go to Step 32 |
26 | 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 41 | -- |
27 | 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 41 | -- |
28 | Test the off blower motor control circuit for a short to voltage. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 41 | Go to Step 33 |
29 | Inspect for poor connections at the harness connector of the A/C high 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 41 | Go to Step 35 |
30 | 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 41 | Go to Step 37 |
31 | 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 in Wiring Systems. Did you find and correct the condition? | Go to Step 41 | Go to Step 36 |
32 | 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 41 | Go to Step 38 |
33 | 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 41 | Go to Step 39 |
34 | 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 41 | Go to Step 40 |
35 | Replace the A/C high pressure switch. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement in Heating, Ventilation, and Air Conditioning. Did you complete the replacement? | Go to Step 41 | -- |
Replace the evaporator temperature sensor. Refer to Air Conditioning Evaporator Core Replacement in Heating, Ventilation and Air Conditioning. Did you complete the replacement? | Go to Step 41 | -- | |
37 | Replace the A/C compressor clutch relay. Did you complete the replacement? | Go to Step 41 | -- |
38 | Replace the A/C compressor clutch coil. Refer to Air Conditioning Compressor Replacement in Heating, Ventilation, and Air Conditioning. Did you complete the replacement? | Go to Step 41 | -- |
39 | Replace the HVAC control module. Refer to HVAC Control Module Replacement . Did you complete the replacement? | Go to Step 41 | -- |
40 |
Important: Perform the reprogramming procedure for the PCM. Replace the PCM. Refer to Powertrain Control Module Replacement in Engine Controls - 3.4L. Did you complete the replacement? | Go to Step 41 | -- |
41 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 4 |