Diagnostic Aids
The air conditioning (A/C) compressor clutch will not engage under the following conditions:
| • | The A/C high side line pressure is over 2 413 kPa (350 psi). |
| • | The throttle angle is at 100 percent. |
| • | A/C compressor temperature switch contacts are open. |
| • | The engine speed is more than 5,500 RPM. |
| • | The engine coolant temperature (ECT) is more than 123°C (253°F). |
| • | The evaporator core temperature is less than 0°C (32°F). |
| • | The engine is idling at a low unstable RPM. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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The A/C compressor output is disabled if the engine is idling at a low unstable RPM.
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The A/C compressor relay output is disabled if the engine coolant temperature is above 123°C (253°F). The check gages indicator will illuminate at this temperature.
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These actions will enable the A/C compressor to operate.
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This test ensures that there is sufficient refrigerant in the A/C system. The specific values come from the A/C System Performance Test in Heating, Ventilation and Air Conditioning.
Step | Action | Values | 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 when 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 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
Does the engine idle at a steady RPM? | -- | Go to Step 3 | Go to 30136 in Engine Controls - 4.8L, 5.3L, and 6.0L | |
Is the check gages indicator illuminated? | -- | Go to Step 4 | Go to Step 5 | |
4 |
Does the ECT parameter display greater than the specified value? | 123°C (253°F) | Go to Engine Overheating in Engine Cooling | Go to Step 5 |
|
Important: For A/C compressor operation, the evaporator core temperature must be above 0°C (32°F).
Does the A/C compressor clutch engage? | -- | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 6 | |
6 |
Does the scan tool indicate that the A/C Request Signal parameter displays Yes? | -- | Go to Step 7 | Go to Step 12 |
Are the low and the high side pressure values within the allowable limits for the recorded ambient air temperature and are the pressure values within 103 kPa (15 psi) of each other? | Above 16°C (60°F) 345 kPa (50 psi) Above 24°C (75°F) 483 kPa (70 psi) Above 33°C (90°F) 690 kPa (100 psi) | Go to Step 8 | Go to Leak Testing in Heating, Ventilation and Air Conditioning | |
8 |
Does the test lamp illuminate? | -- | Go to Step 9 | Go to Step 18 |
9 | Probe the ignition 3 voltage circuit of the A/C compressor clutch relay with a test lamp connected to a good ground. Does the test lamp illuminate? | -- | Go to Step 10 | Go to Step 19 |
10 |
Does the test lamp illuminate? | -- | Go to Step 14 | Go to Step 11 |
11 | Connect a 10-amp fused jumper between the battery positive voltage circuit and the A/C compressor clutch supply voltage circuit of the A/C compressor clutch relay. Does the A/C compressor clutch engage? | -- | Go to Step 20 | Go to Step 15 |
12 |
Does the test lamp illuminate? | -- | Go to Step 13 | Go to Step 16 |
13 |
Does the scan tool indicate the A/C Request Signal parameter is Yes? | -- | Go to Step 21 | Go to Step 17 |
14 | Test the A/C compressor clutch relay control circuit of the A/C compressor clutch relay for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 32 | Go to Step 23 |
15 | 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 in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 32 | Go to Step 24 |
16 | Test the A/C request signal circuit of the HVAC control module for a short to ground, a high resistance, and for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 32 | Go to Step 25 |
17 | Test the A/C request signal circuit of the RDM for a short to ground, a high resistance, and for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 32 | Go to Step 22 |
18 | Repair the battery positive voltage circuit of the A/C compressor clutch relay. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 32 | -- |
19 | Repair the ignition 3 voltage circuit of the A/C compressor clutch relay. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 32 | -- |
20 | 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 32 | Go to Step 26 |
21 | Inspect for poor connections at 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 32 | Go to Step 28 |
22 | Inspect for poor connections at the RDM. 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 32 | Go to Step 27 |
23 | Inspect for poor connections at 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 32 | Go to Step 29 |
24 | Inspect for poor connections at 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 32 | Go to Step 30 |
25 | Inspect for poor connections at 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 32 | Go to Step 31 |
26 | Replace the A/C compressor clutch relay. Did you complete the replacement? | -- | Go to Step 32 | -- |
27 | Replace the RDM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 32 | -- |
28 | Replace the evaporator temperature sensor. Refer to Evaporator Temperature Sensor Replacement in Heating, Ventilation and Air Conditioning. Did you complete the replacement? | -- | Go to Step 32 | -- |
29 | Replace the PCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 32 | -- |
30 | Replace the A/C compressor. Refer to Air Conditioning Compressor Replacement in Heating, Ventilation and Air Conditioning. Did you complete the replacement? | -- | Go to Step 32 | -- |
31 | Replace the HVAC control module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 32 | -- |
32 | Operate the system in order to verify the repair. Did you correct the condition? | -- | System OK | Go to Step 5 |
