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Test Description

WARNING: This page is about a different car, the 2004 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.

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).
  1. 3:  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.
  2. 6:  The HVAC control module is inoperative when the module does not respond to any operator control requests to enable the A/C compressor. The blower motor may still operate independent of the A/C controls.
HVAC Compressor Clutch Does Not Engage

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 perform the HVAC Diagnostic System Check? Go to Step 2  Go to Diagnostic System Check - HVAC Systems - Automatic 
2 
  1. Install a scan tool.
  2. Start the engine.
  3. With a scan tool, observe the ECT Sensor parameter in the Powertrain data list.
Does the scan tool indicate that the ECT Sensor parameter is below 121°C (250°F)?		 Go to Step 3  Go to Engine Overheating in Engine Cooling
3 
IMPORTANT: For A/C compressor operation, 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 request switch in the ON position.
  4. Place the air temperature switch in the coldest position.
Does the A/C compressor operate?		 Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems Go to Step 4 
4
  1. Park the vehicle inside or in the shade.
  2. Open the windows in order to ventilate the interior of the vehicle.
  3. If the A/C system was operating, allow the A/C system to equalize, about 2 minutes.
  4. Turn OFF the ignition.
  5. Install the J 43600  ACR 2000.
  6. Record the ambient air temperature at the vehicle.
  7. Record readings of the low and high side STATIC pressures.
  8. Compare the pressure values with the specifications for the ambient air temperature. Refer to Air Conditioning (A/C) System Performance Test in Heating, Ventilation and Air Conditioning.
Does the system pass the A/C System Performance Test?		 Go to Step 5  Go to Leak Testing in Heating, Ventilation and Air Conditioning
5
  1. Turn ON the ignition, with the engine OFF.
  2. With a scan tool, observe the A/C High Side Pressure parameter in the powertrain data 2 list.
  3. Compare the A/C High Side Pressure parameter on the scan tool to the high side pressure value on the ACR2000.
Are the pressure values within 103 kPa (15 psi) of each other?		 Go to Step 6  Go to Step 16 
6  Is the HVAC control module inoperative? Go to Step 15  Go to Step 7 
7
  1. Start the engine.
  2. With a scan tool, observe the A/C Request Signal parameter in the powertrain data list.
  3. Place the air temperature switch in the coldest position.
  4. 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 8  Go to Step 27 
8 With a scan tool, observe the A/C Relay Command status in the powertrain data list.
Does the scan tool indicate that the A/C Relay Command status is ON?		 Go to Step 9  Go to Step 28 
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
  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the coil side 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 11  Go to Step 23 
11
  1. Connect a test lamp between the control circuit of the A/C compressor clutch relay and the coil side voltage supply circuit of the A/C compressor clutch relay.
  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 25  Go to Step 12 
12 Does the test lamp remain illuminated with each command? Go to Step 19  Go to Step 18 
13
  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch relay.
  3. Probe the switch side 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 14  Go to Step 22 
14
  1. Connect a 10 amp fused jumper wire between the switch side voltage circuit of the A/C compressor clutch relay and the A/C compressor clutch 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 25  Go to Step 20 
15 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 34  Go to Step 17 
16 Test the low reference circuit of the A/C refrigerant 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 34  Go to Step 24 
17 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 34  Go to Step 27 
18 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 34  Go to Step 28 
19 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 34  Go to Step 28 
20 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 34  Go to Step 21 
21 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 34  Go to Step 26 
22 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 34  -
23 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 34  -
24 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 in Wiring Systems.
Did you find and correct the condition?		 Go to Step 34  Go to Step 29 
25 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 34  Go to Step 30 
26 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 34  Go to Step 31 
27 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 34  Go to Step 32 
28 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 34  Go to Step 33 
29 Replace the A/C refrigerant pressure sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement in Heating, Ventilation and Air Conditioning.
Did you complete the replacement?		 Go to Step 34  -
30 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 34  -
31 Replace the A/C compressor clutch coil. Refer to Compressor Clutch Coil Removal and Compressor Clutch Coil Install in Heating, Ventilation and Air Conditioning.
Did you complete the replacement?		 Go to Step 34  -
32
IMPORTANT: Perform the recalibration 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 34  -
33
IMPORTANT: Perform the programming procedure for the PCM.
Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement in Engine Controls.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 4 
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