LEMON Manuals: Even more car manuals for everyone
Home >> Chevrolet >> 2006 >> Cobalt LTZ >> Repair and Diagnosis >> External Pages >> Different car >> Section 659 (HVAC System - Manual) >> Diagnostic Information and Procedures >> HVAC Compressor Clutch Does Not Engage >> Test Description

Test Description

WARNING: This page is about a different car, the 2007 Pontiac G5 Pursuit, 2007 Pontiac G5, and 2007 Chevrolet Cobalt. 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 123°C (253°F). The instrument panel engine coolant gage will indicate overheating.
  1. 3:  Place the mode switch in any position except OFF, and place the air temperature control switch in a cold setting. Use the believe mode for consistent testing of the A/C system operation.
  2. 6:  The HVAC control module is inoperative if the module does not respond to any operator control requests.
  1. 14:  Be sure to verify the engine control module (ECM) or powertrain control module (PCM) engine grounds are secure and clean.
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 if 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
2 
  1. Start the engine.
  2. Observe the instrument panel coolant temperature gage.
Is the engine coolant temperature gage indicating an over heat status?		 Go to Engine Overheating 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 request switch in the ON position.
  4. Place the air temperature switch in the coldest position.
Does the A/C compressor clutch engage?		 Go to Testing for Intermittent Conditions and Poor Connections Go to Step 4 
4
  1. Open the window in order to ventilate the interior of the vehicle.
  2. If the A/C system was operating, then wait for approximately 2 minutes.
  3. Turn OFF the ignition.
  4. Install the J 43600  ACR 2000 Air Conditioning Service Center.
  5. Record the ambient air temperature at the vehicle.
  6. Record readings of the low and high side STATIC pressures.
  7. Compare the low side pressure values and the high side pressure values with the allowable limits for the recorded ambient air temperature. Refer to Air Conditioning (A/C) System Performance Test (RPO LE5) or Air Conditioning (A/C) System Performance Test (RPO LSJ) or Air Conditioning (A/C) System Performance Test (RPOs L61, LE5) .
Are the 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
5
  1. Turn ON the ignition, with the engine OFF.
  2. With a scan tool, observe the A/C High Side Pressure Sensor parameter in the engine control module data list.
  3. Compare the scan tool A/C high side pressure parameter to the high side pressure values on the J 43600  .
Are the high side pressure values within 103 kPa (15 psi) of each other?		 Go to Step 6  Go to Step 23 
6  Is the HVAC control module inoperative? Go to Step 16  Go to Step 7 
7
  1. Start the engine.
  2. With a scan tool, observe the A/C Request Signal parameter in the ECM 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 10  Go to Step 8 
8
  1. Start the engine.
  2. With a scan tool, observe the A/C Switch parameter in the body control module (BCM) 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 Switch parameter is ON?		 Go to Step 9  Go to Step 18 
9
  1. Turn OFF the ignition.
  2. Test the A/C request signal circuit for a short to voltage, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 Go to Step 39  Go to Step 10 
10 With a scan tool, command the A/C compressor clutch relay ON and OFF.
Does the clutch relay turn ON and OFF with each command?		 Go to Step 14  Go to Step 11 
11
  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 of the voltage supply circuit with a test lamp that is connected to a good ground.
Does the test lamp illuminate?		 Go to Step 12  Go to Step 26 
12
  1. Connect a test lamp between the control circuit and the coil side of the voltage supply 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 13 
13 Does the test lamp remain illuminated with each command? Go to Step 21  Go to Step 20 
14 
  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch relay.
  3. Probe the switch side of the voltage supply circuit with a test lamp that is connected to a good ground.
Does the test lamp illuminate?		 Go to Step 15  Go to Step 25 
15
  1. Connect a 10-amp fused jumper between the switch side voltage circuit of the clutch relay and the supply voltage circuit of the clutch.
  2. Turn ON the ignition, with the engine OFF.
Does the A/C compressor clutch engage?		 Go to Step 28  Go to Step 22 
16 Test the ignition 3 voltage circuit of the HVAC control assembly for a short to ground, a high resistance, or an open. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 Go to Step 39  Go to Step 17 
17 Test the ground circuit of the HVAC control assembly for an open. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 Go to Step 39  Go to Step 30 
18
  1. Start the engine.
  2. Place the A/C request in the ON position.
  3. Measure the voltage on the request circuit at the BCM to a good ground.
Does the value measure near battery voltage?		 Go to Step 31  Go to Step 19 
19 Test the A/C request signal circuit for a high resistance, an open, or a short to ground. Refer to Circuit Testing and Wiring Repairs .
Did you complete the repair?		 Go to Step 39  Go to Step 30 
20 Test the control circuit of the A/C compressor clutch relay for an open. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 Go to Step 39  Go to Step 28 
21 Test the control circuit of the A/C compressor clutch relay for a short to ground. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 Go to Step 39  Go to Step 28 
22 Test the 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 .
Did you find and correct the condition?		 Go to Step 39  Go to Step 24 
23 Test the ground circuit of the A/C refrigerant pressure sensor for an open. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 Go to Step 39  Go to Step 27 
24 Test the ground circuit of the A/C compressor clutch for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 Go to Step 39  Go to Step 29 
25 Repair the switch side voltage supply circuit of the A/C compressor clutch relay. Refer to Wiring Repairs .
Did you complete the repair?		 Go to Step 39  -
26 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 39  -
27 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 .
Did you find and correct the condition?		 Go to Step 39  Go to Step 33 
28 Inspect for poor connections at the A/C compressor clutch relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?		 Go to Step 39  Go to Step 34 
29 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 .
Did you find and correct the condition?		 Go to Step 39  Go to Step 35 
30 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 .
Did you find and correct the condition?		 Go to Step 39  Go to Step 36 
31 Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?		 Go to Step 39  Go to Step 37 
32 Inspect for poor connections at the harness connector of the ECM or PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?		 Go to Step 39  Go to Step 38 
33 Replace the A/C refrigerant pressure sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement .
Did you complete the replacement?		 Go to Step 39  -
34 Replace the A/C compressor clutch relay.
Did you complete the replacement?		 Go to Step 39  -
35 Replace the A/C compressor clutch assembly. Refer to Compressor Clutch Assembly Replacement .
Did you complete the replacement?		 Go to Step 39  -
36 Replace the HVAC control module. Refer to Control Module References for replacement, setup, and programming.
Did you complete the replacement?		 Go to Step 39  -
37 Replace the BCM. Refer to Control Module References for replacement, setup, and programming.
Did you complete the replacement?		 Go to Step 39  -
38 Replace the ECM or PCM. Refer to Control Module References for replacement, setup, and programming.
Did you complete the replacement?		 Go to Step 39  -
39 Operate the system in order to verify the repair.
Did you correct the condition?		 System OK Go to Step 4 
scientia non olet · About LEMON Manuals