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Test Description

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The numbers below refer to the step numbers on the diagnostic table.

  1. 2:  The A/C compressor relay output is disabled if engine coolant temperature is above 121°C (250°F). The engine coolant indicator will illuminate at this temperature.
  2. 3:  These actions will enable the A/C compressor to operate.
  3. 4:  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.
  4. 5:  If the HVAC control module does not respond to requests, the module is inoperative.
  5. 6:  This action ensures that the powertrain control module (PCM) is getting an A/C request from the HVAC control module.
  6. 7:  If the A/C request LED does not illuminate the HVAC control module is not grounding the A/C request signal circuit.
  7. 8:  Since the A/C system pressure has been verified in Step 4 this step will verify the integrity of the A/C request signal circuits, if the A/C Request Signal parameter is Yes then there is a concern with the A/C high pressure switch.
  8. 10:  Since the A/C system pressure has been verified in Step 4 this step will verify the integrity of the A/C low pressure signal circuit and the ground circuit of the A/C low pressure switch, if the A/C Compressor Cycling Switch parameter is Normal then there is a concern with the A/C low pressure switch.
  9. 14:  If the test lamp remains illuminated the A/C compressor clutch relay control circuit is shorted to ground.
  10. 18:  If the fused jumper opens during this step the A/C compressor clutch supply voltage circuit is short to ground.
  11. 26:  Ensure that both A/C request signal circuits of the A/C high pressure switch are tested for listed conditions.
HVAC Compressor Clutch Does Not Engage

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 perform the HVAC Diagnostic System Check? Go to Step 2  Go to Diagnostic System Check - HVAC Systems - Automatic 
2 
  1. Start the engine.
  2. Observe the coolant temperature indicator.
Is the engine coolant temperature indicator illuminated?		 Go to ENGINE COOLANT TEMPERATURE INDICATOR ALWAYS ON Go to Step 3 
3 
    IMPORTANT: For A/C compressor operation, the ambient air temperature must be above 3°C (38°F).
  1. Start the engine.
  2. Place the blower motor switch in the maximum speed position.
  3. Place the A/C switch in the ON position.
  4. Place the air temperature control switch in the coldest position.
Does the A/C compressor operate?		 Go to TESTING FOR INTERMITTENT AND POOR CONNECTIONS Go to Step 4 
4 
  1. Park the vehicle inside or out of direct sunlight.
  2. Open the window in order to ventilate the interior of the vehicle.
  3. If the A/C system was operating, wait for approximately 2 minutes.
  4. Turn OFF the ignition.
  5. Install J 43600  .
  6. Record the ambient temperature at the vehicle.
  7. Record the low side and the high side STATIC pressures.
  8. Compare the pressure values with the specifications for the ambient air temperature. Refer to A/C SYSTEM PERFORMANCE TEST .
Are the pressure values within the specifications for the ambient air temperature, and within 103 kPa (15 psi) of each other?		 Go to Step 5  Go to LEAK TESTING
5  Is the HVAC control module inoperative? Go to Step 20  Go to Step 6 
6 
  1. Start the engine.
  2. With a scan tool, observe the A/C Request Signal parameter in the powertrain data list.
  3. Place the A/C request switch in the ON position.
Does the scan tool indicate that the A/C Request Signal parameter is Yes?		 Go to Step 9  Go to Step 7 
7  Does the A/C request indicator illuminate? Go to Step 8  Go to Step 31 
8 
  1. Turn OFF the ignition.
  2. Disconnect the A/C high pressure switch.
  3. Connect a 3-ampere fused jumper between the A/C request circuits at the A/C high pressure switch connector.
  4. Start the engine.
  5. With a scan tool, observe the A/C Request Signal parameter.
  6. Place the A/C request switch in the ON position.
Does the scan tool indicate that the A/C Request Signal parameter is Yes?		 Go to Step 32  Go to Step 26 
9 Does the scan tool indicate the A/C Compressor Cycling Switch parameter is Normal? Go to Step 11  Go to Step 10 
10 
  1. Turn OFF the ignition.
  2. Disconnect the A/C low pressure switch.
  3. Connect a 3-ampere fused jumper between the low A/C pressure sensor signal and the ground circuits.
  4. Start the engine.
  5. With a scan tool, observe the A/C Compressor Cycling Switch parameter.
Does the scan tool indicate the A/C Compressor Cycling Switch parameter is Normal?		 Go to Step 29  Go to Step 22 
11 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 12 
12
  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Using a test lamp that is connected to a good ground, probe the coil side of the voltage circuit of the A/C compressor clutch relay.
Does the test lamp illuminate?		 Go to Step 13  Go to Step 27 
13
  1. Connect a test lamp on the A/C compressor clutch relay between the control circuit and the coil side of the voltage circuit.
  2. With a scan tool, command the A/C compressor clutch relay ON and OFF.
Does the test lamp turn ON and OFF with each command?		 Go to Step 28  Go to Step 14 
14  Does the test lamp remain illuminated with each command? Go to Step 16  Go to Step 15 
15 Test the control circuit of the A/C compressor clutch relay for an open. Refer to CIRCUIT TESTING and to WIRING REPAIRS .
Did you find and correct the condition?		 Go to Step 40  Go to Step 33 
16 Test the control circuit of the A/C compressor clutch relay for a short to ground. Refer to CIRCUIT TESTING and to WIRING REPAIRS .
Did you find and correct the condition?		 Go to Step 40  Go to Step 33 
17
  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch relay.
  3. Probe the switch side of the voltage supply 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 18  Go to Step 19 
18 
  1. Connect a 10-ampere fused jumper between battery positive voltage and the supply voltage circuit of the A/C compressor clutch.
  2. Turn ON the ignition, with the engine OFF.
Does the A/C compressor clutch engage?		 Go to Step 28  Go to Step 24 
19 Repair the switch side of the voltage supply circuit of the A/C compressor clutch relay. Refer to WIRING REPAIRS .
Did you complete the repair?		 Go to Step 40  -
20 Test the ignition 3 voltage circuit of the HVAC control module for a short to ground, for a high resistance, or for an open. Refer to CIRCUIT TESTING and to WIRING REPAIRS .
Did you find and correct the condition?		 Go to Step 40  Go to Step 21 
21 Test the ground circuit of the HVAC control module for an open. Refer to CIRCUIT TESTING and to WIRING REPAIRS .
Did you find and correct the condition?		 Go to Step 40  Go to Step 31 
22 Test the signal circuit of the A/C low pressure switch for a high resistance or for an open. Refer to CIRCUIT TESTING and to WIRING REPAIRS .
Did you find and correct the condition?		 Go to Step 40  Go to Step 23 
23 Test the ground circuit of the A/C low pressure switch for a high resistance or for an open. Refer to CIRCUIT TESTING and to WIRING REPAIRS .
Did you find and correct the condition?		 Go to Step 40  Go to Step 33 
24 Test the supply voltage circuit at the A/C compressor clutch for a short to ground, for a high resistance, or for an open. Refer to CIRCUIT TESTING and to WIRING REPAIRS .
Did you find and correct the condition?		 Go to Step 40  Go to Step 25 
25 Test the ground circuit of the A/C compressor clutch for a high resistance or for an open. Refer to CIRCUIT TESTING and to WIRING REPAIRS .
Did you find and correct the condition?		 Go to Step 40  Go to Step 30 
26 
  1. Turn OFF the ignition.
  2. Reconnect the A/C high pressure switch.
  3. Test the both A/C request signal circuits of the A/C high pressure switch for a short to ground, for a high resistance, or for an open. Refer to CIRCUIT TESTING and to WIRING REPAIRS .
Did you find and correct the condition?		 Go to Step 40  Go to Step 33 
27 Repair the coil side of the voltage supply circuit of the A/C compressor clutch relay. Refer to WIRING REPAIRS .
Did you complete the repair?		 Go to Step 40  -
28 Inspect for poor connections at the A/C compressor clutch relay. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and to CONNECTOR REPAIRS .
Did you find and correct the condition?		 Go to Step 40  Go to Step 34 
29 Inspect for poor connections at the harness connector of the A/C low pressure switch. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and to CONNECTOR REPAIRS .
Did you find and correct the condition?		 Go to Step 40  Go to Step 35 
30 Inspect for poor connections at the harness connector of the A/C compressor clutch. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and to CONNECTOR REPAIRS .
Did you find and correct the condition?		 Go to Step 40  Go to Step 37 
31 Inspect for poor connections at the harness connector of the HVAC control module. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and to CONNECTOR REPAIRS .
Did you find and correct the condition?		 Go to Step 40  Go to Step 38 
32 Inspect for poor connections at the harness connector of the A/C high pressure switch. Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and to CONNECTOR REPAIRS .
Did you find and correct the condition?		 Go to Step 40  Go to Step 36 
33 Inspect for poor connections at the harness connector of the powertrain control module (PCM). Refer to TESTING FOR INTERMITTENT AND POOR CONNECTIONS and to CONNECTOR REPAIRS .
Did you find and correct the condition?		 Go to Step 40  Go to Step 39 
34 Replace the A/C compressor clutch relay. Refer to COMPRESSOR RELAY REPLACEMENT .
Did you complete the replacement?		 Go to Step 40  -
35 Replace the A/C low pressure switch. Refer to A/C LOW PRESSURE SWITCH REPLACEMENT .
Did you complete the replacement?		 Go to Step 40  -
36 Replace the A/C high pressure switch. Refer to A/C HIGH PRESSURE SWITCH .
Did you complete the replacement?		 Go to Step 40  -
37 Replace the A/C compressor clutch coil. Refer to A/C COMPRESSOR CLUTCH RELAY.
Did you complete the replacement?		 Go to Step 40  -
38
IMPORTANT: Perform the calibration procedure for the HVAC control module.
Replace the HVAC control module. Refer to HVAC Control Module Replacement .Did you complete the replacement?		 Go to Step 40  -
39
IMPORTANT: Program the PCM.
Replace the Powertrain Control Module (PCM). Refer to POWERTRAIN CONTROL MODULE .Did you complete the replacement?		 Go to Step 40  -
40 Operate the system in order to verify the repair.
Did you correct the condition?		 System OK Go to Step 4 
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