The numbers below refer to the step numbers on the diagnostic table.
For the purpose of this and future steps where A/C operation is necessary, bi-level mode is used for consistent testing.
This step ensures that there is a proper amount of refrigerant in the A/C system to be able to close the A/C pressure switches.
There is two control circuits for the coil side of the A/C compressor clutch relay. The A/C compressor clutch control circuit, which provides the relay with ignition 3 voltage, is the correct circuit to test.
An audible click sound will be made by the A/C compressor clutch if it engages.
If the fused jumper opens during this test, the circuit or ECM input is shorted to ground.
If circuit is shorted to ground, ensure to inspect the HVAC 20 ampere circuit breaker
If no concern with the circuit, the engine control module (ECM) is pulling the circuit to ground. The ECM can not disable the A/C compressor relay.
If the A/C fuse is open ensure to test the battery positive circuit, A/C compressor clutch supply voltage circuit, and the A/C compressor clutch coil for short to ground.
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 review the HVAC operation and perform the necessary inspections? | Go to Step 2 | |||||||
Does the A/C compressor operate? | Go to Testing for Intermittent Conditions and Poor Connections | Go to Step 3 | |||||||
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 4 | Go to Leak Testing | |||||||
4 |
Does the scan tool indicate that the A/C Request Signal parameter is Yes? | Go to Step 5 | Go to Step 10 | ||||||
Does the test lamp illuminate? | Go to Step 6 | Go to Step 19 | |||||||
6 | Probe the A/C low pressure switch signal circuit of the A/C compressor clutch relay with a test lamp that is connected to battery positive voltage. Does the test lamp illuminate? | Go to Step 7 | Go to Step 12 | ||||||
7 |
Does the resistance measure near 77 ohms? | Go to Step 8 | Go to Step 28 | ||||||
8 | Probe the battery positive voltage circuit of the A/C compressor clutch relay with a test lamp that is connected to a good ground. Does the test lamp illuminate? | Go to Step 9 | Go to Step 20 | ||||||
Does the A/C compressor clutch engage? | Go to Step 22 | Go to Step 14 | |||||||
10 |
Does the test lamp illuminate? | Go to Step 11 | Go to Step 16 | ||||||
Does the scan tool indicate that the A/C Request Signal parameter is Yes? | Go to Step 23 | Go to Step 17 | |||||||
12 |
Does the test lamp illuminate? | Go to Step 13 | Go to Step 21 | ||||||
13 |
Does the test lamp illuminate? | Go to Step 24 | Go to Step 18 | ||||||
14 | Test the A/C compressor clutch supply voltage circuit of the A/C compressor clutch for the following conditions:
Refer to Circuit Testing and to Wiring Repairs . Did you find and correct the condition? | Go to Step 34 | Go to Step 15 | ||||||
15 | Test the ground circuit of the A/C compressor clutch for the following conditions:
Refer to Circuit Testing and to Wiring Repairs . Did you find and correct the condition? | Go to Step 34 | Go to Step 25 | ||||||
Test the A/C request signal circuit of the A/C high pressure switch for the following conditions:
Refer to Circuit Testing and to Wiring Repairs . Did you find and correct the condition? | Go to Step 34 | Go to Step 26 | |||||||
Test the A/C compressor clutch relay control circuit of the A/C high pressure switch for the following conditions:
Refer to Circuit Testing and to Wiring Repairs . Did you find and correct the condition? | Go to Step 34 | Go to Step 27 | |||||||
18 | Test the A/C low pressure switch signal circuit of the A/C low pressure switch for the following conditions:
Refer to Circuit Testing and to Wiring Repairs . Did you find and correct the condition? | Go to Step 34 | Go to Step 22 | ||||||
19 | Repair the A/C compressor clutch control circuit. Refer to Wiring Repairs . Did you complete the repair? | Go to Step 34 | -- | ||||||
Repair the battery positive voltage circuit of the A/C compressor clutch relay. Refer to Wiring Repairs . Did you complete the repair? | Go to Step 34 | -- | |||||||
21 | Repair the ground circuit of the A/C low pressure switch. Refer to Wiring Repairs . Did you complete the repair? | Go to Step 34 | -- | ||||||
22 | Inspect for poor connections at the harness connector of the A/C compressor clutch relay. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs . Did you find and correct the condition? | Go to Step 34 | Go to Step 28 | ||||||
23 | Inspect for poor connections at the harness connector of the A/C high pressure switch. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs . Did you find and correct the condition? | Go to Step 34 | Go to Step 29 | ||||||
24 | Inspect for poor connections at the harness connector of the A/C low pressure switch. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs . Did you find and correct the condition? | Go to Step 34 | Go to Step 30 | ||||||
25 | Inspect for poor connections at the harness connector of the A/C compressor clutch coil. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs . Did you find and correct the condition? | Go to Step 34 | Go to Step 31 | ||||||
26 | Inspect for poor connections at the harness connector of the HVAC control assembly. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs . Did you find and correct the condition? | Go to Step 34 | Go to Step 32 | ||||||
27 | Inspect for poor connections at the harness connector of the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs . Did you find and correct the condition? | Go to Step 34 | Go to Step 33 | ||||||
28 | Replace the A/C compressor clutch relay. Refer to Compressor Relay Replacement . Did you complete the replacement? | Go to Step 34 | -- | ||||||
29 | Replace the A/C high pressure switch. Refer to Air Conditioning (A/C) High Pressure Switch Replacement . Did you complete the replacement? | Go to Step 34 | -- | ||||||
30 | Replace the A/C low pressure switch. Refer to Air Conditioning Cycling Switch Replacement . Did you complete the replacement? | Go to Step 34 | -- | ||||||
31 | Replace the A/C compressor clutch coil or A/C compressor. Refer to the appropriate repair procedure: Did you complete the replacement? | Go to Step 34 | -- | ||||||
32 | Replace the HVAC control assembly. Refer to Heater and Air Conditioning Control Replacement . Did you complete the replacement? | Go to Step 34 | -- | ||||||
33 | Replace the ECM. Refer to Engine Control Module Replacement/Restore Fuel Rate Data . 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 3 |
The numbers below refer to the step numbers on the diagnostic table.
The A/C compressor relay output is disabled if engine coolant temperature (ECT) is above 121°C (250°F).
For the purpose of this and future steps where A/C operation is necessary, bi-level mode is used for consistent testing.
With each command, an audible click sound should be made.
There are 2 A/C request signal circuits that connect to the A/C high pressure switch. The circuit that is to be tested is wired between the HVAC control assembly and the A/C high pressure switch.
There are 2 A/C request signal circuits that connect to the A/C high pressure switch. The circuit that is to be tested is wired between the engine control module (ECM)/powertrain control module (PCM) and the A/C high pressure switch.
There are 2 A/C request signal circuits that connect to the A/C high pressure switch. The circuit that is to be tested is wired between the HVAC control assembly and the A/C high pressure switch.
There are 2 A/C request signal circuits that connect to the A/C high pressure switch. The circuit that is to be tested is wired between the ECM/PCM and the A/C high pressure switch.
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 review the HVAC operation and perform the necessary inspections? | Go to Step 2 | |||||||
Does the ECT Sensor parameter indicate a value over 121°C (250°F)? | Go to Symptoms - Engine Cooling in Engine Cooling | Go to Step 3 | |||||||
Important: For A/C compressor operation, outside 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 |
Are the low and high side pressure values within the allowable limits for the recorded ambient air temperature (AAT), and within 103 kPa (15 psi) of each other? | Go to Step 5 | Go to Leak Testing in Heating, Ventilation and Air Conditioning | ||||||
5 |
Does the scan tool indicate that the A/C Request Signal parameter is YES? | Go to Step 6 | Go to Step 11 | ||||||
6 | With a scan tool, observe the A/C Compressor Cycling Switch parameter in the Powertrain Engine data list. Does the scan tool indicate that the A/C Compressor Cycling Switch parameter is YES? | Go to Step 7 | Go to Step 13 | ||||||
Does the A/C compressor clutch relay turn ON and OFF with each command? | Go to Step 9 | Go to Step 8 | |||||||
8 |
Does the test lamp illuminate with each command? | Go to Step 26 | Go to Step 15 | ||||||
9 | Probe the battery positive voltage circuit of the A/C compressor clutch relay with a test lamp that is connected to a good ground. Does the test lamp illuminate? | Go to Step 10 | Go to Step 23 | ||||||
10 |
Does the A/C compressor clutch engage? | Go to Step 26 | Go to Step 17 | ||||||
Does the test lamp illuminate? | Go to Step 12 | Go to Step 20 | |||||||
Does the scan tool indicate that the A/C Request Signal parameter is YES? | Go to Step 27 | Go to Step 21 | |||||||
13 |
Does the test lamp illuminate? | Go to Step 14 | Go to Step 24 | ||||||
14 |
Does the scan tool indicate that the A/C Compressor Cycling Switch parameter is YES? | Go to Step 28 | Go to Step 22 | ||||||
15 |
Does the test lamp illuminate with each command? | Go to Step 25 | Go to Step 16 | ||||||
16 | Test the A/C compressor clutch relay control circuit of the A/C high pressure switch for the following conditions:
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 38 | Go to Step 31 | ||||||
17 |
Does the test lamp illuminate? | Go to Step 19 | Go to Step 18 | ||||||
18 | Test the A/C compressor clutch supply voltage circuit of the A/C compressor clutch for the following conditions:
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 38 | Go to Step 29 | ||||||
19 | Test the ground circuit of the A/C compressor clutch for the following conditions:
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 38 | Go to Step 29 | ||||||
Test the A/C request signal circuit of the HVAC control assembly for the following conditions:
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 38 | Go to Step 30 | |||||||
Test the A/C request signal circuit of the engine control module (ECM)/powertrain control module (PCM) for the following conditions:
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 38 | Go to Step 31 | |||||||
22 | Test the A/C low pressure switch signal circuit of the ECM/PCM for the following conditions:
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 38 | Go to Step 31 | ||||||
23 | Repair the battery positive circuit of the A/C compressor clutch relay. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 38 | -- | ||||||
24 | Repair the ground circuit of the A/C low pressure switch. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 38 | -- | ||||||
25 | Repair the ignition 3 voltage circuit of the A/C compressor clutch relay. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 38 | -- | ||||||
26 | Inspect for poor connections at the harness connector of 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 38 | Go to Step 32 | ||||||
27 | Inspect for poor connections at the harness connector of the A/C high pressure switch. 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 38 | Go to Step 33 | ||||||
28 | Inspect for poor connections at the harness connector of the A/C low pressure switch. 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 38 | Go to Step 34 | ||||||
29 | Inspect for poor connections at the harness connector of the A/C compressor clutch coil. 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 38 | Go to Step 35 | ||||||
30 | Inspect for poor connections at the harness connector of the HVAC control assembly. 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 38 | Go to Step 36 | ||||||
31 | Inspect for poor connections at the harness connector of the ECM/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 38 | Go to Step 37 | ||||||
32 | 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 38 | -- | ||||||
33 | Replace the A/C high pressure switch. Refer to Air Conditioning (A/C) High Pressure Switch Replacement in Heating, Ventilation and Air Conditioning. Did you complete the replacement? | Go to Step 38 | -- | ||||||
34 | Replace the A/C low pressure switch. Refer to Air Conditioning (A/C) Low Pressure Switch Replacement in Heating, Ventilation and Air Conditioning. Did you complete the replacement? | Go to Step 38 | -- | ||||||
35 | Replace the A/C compressor clutch coil or A/C compressor. Refer to the appropriate repair procedure:
Did you complete the replacement? | Go to Step 38 | -- | ||||||
36 | Replace the HVAC control assembly. Refer to Heater and Air Conditioning Control Replacement . Did you complete the replacement? | Go to Step 38 | -- | ||||||
37 | Replace the ECM/PCM. Refer to the appropriate procedure:
Did you complete the replacement? | Go to Step 38 | -- | ||||||
38 | Operate the system in order to verify the repair. Did you correct the condition? | Go to Step 2 | -- |