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Test Description

WARNING: This page is about a different car, the 2004 Pontiac Aztek and 2004 Buick Rendezvous. 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). The engine coolant indicator will illuminate at this temperature.
  1. 3:  Place the mode switch in any position except OFF, and place the air temperature control switch in a cold setting. Use the bi-level 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.
  3. 40:  The evaporator temperature sensor is replaced as part of the evaporator core.
HVAC Compressor Clutch Does Not Engage

Step Action 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 if 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  Go to Symptoms - HVAC Systems - Manual 
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 in Engine Cooling 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 in Wiring Systems 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, then wait for approximately 2 minutes.
  4. Turn OFF the ignition.
  5. Install the J 43600  ACR 2000 Air Conditioning Service Center.
  6. Record the ambient air temperature at the vehicle.
  7. Record readings of the low and high side STATIC pressures.
  8. 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 .
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 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 Sensor parameter in the powertrain data list
  3. Compare the pressure values with the specifications for the ambient air temperature.
Are the pressure values within specifications for the ambient air temperature, and within 103 kPa (15 psi) of each other?		 Go to Step 6  Go to Step 27 
6  Is the HVAC control module inoperative? Go to Step 19  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 14  Go to Step 8 
8
  1. Start the engine.
  2. With a test lamp, observe the A/C Switch parameter in the body control module (BCM).
  3. Place the air temperature switch in the coldest position.
  4. Place the A/C request switch in the ON position.
Does the test lamp illuminate?		 Go to Step 9  Go to Step 22 
9 Does the A/C request indicator illuminate? Go to Step 10  Go to Step 31 
10
  1. Turn OFF the ignition.
  2. Test the A/C request signal circuit for a short to voltage, for a high resistance, or for an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 46  Go to Step 11 
11
  1. Disconnect the evaporator temperature sensor.
  2. Measure the resistance of the evaporator temperature sensor. Refer to Sensor Resistance Table .
Is the resistance measurement near the values specified in the sensor resistance table?		 Go to Step 12  Go to Step 34 
12 Test the evaporator temperature signal circuit for a short to ground, for a high resistance, or for an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 46  Go to Step 13 
13 Test the low reference circuit for a short to ground, for a high resistance, or for an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 46  Go to Step 36 
14 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 18  Go to Step 15 
15
  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 16  Go to Step 30 
16
  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 33  Go to Step 17 
17 Does the test lamp remain illuminated with each command? Go to Step 25  Go to Step 24 
18
  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 19  Go to Step 29 
19
  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 33  Go to Step 26 
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 in Wiring Systems.
Did you find and correct the condition?		 Go to Step 46  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 in Wiring Systems.
Did you find and correct the condition?		 Go to Step 46  Go to Step 36 
22
  1. Start the engine.
  2. Place the A/C request in the ON position.
  3. Measure the voltage on the request circuit at the Body Control Module (BCM) to a good ground.
Does the value measure near battery voltage?		 Go to Step 37  Go to Step 23 
23 Test the A/C request signal circuit for a high resistance, open or a short to ground. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 Go to Step 46  Go to Step 36 
24 Test the control circuit of the A/C compressor clutch relay for an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 46  Go to Step 38 
25 Test the control circuit of the A/C compressor clutch relay for a short to ground. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 46  Go to Step 38 
26 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 in Wiring Systems.
Did you find and correct the condition?		 Go to Step 46  Go to Step 28 
27 Test the ground circuit of the A/C pressure sensor for an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 46  Go to Step 32 
28 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 in Wiring Systems.
Did you find and correct the condition?		 Go to Step 46  Go to Step 35 
29 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 46  -
30 Repair the coil side of the 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 46  -
31 Test the off blower motor control circuit for a short to voltage. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 46  Go to Step 36 
32 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 to Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 46  Go to Step 39 
33 Inspect for poor connections at the A/C compressor clutch relay. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 46  Go to Step 41 
34 Inspect for poor connections at the harness connector of the evaporator temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 46  Go to Step 40 
35 Inspect for poor connections at the harness connector of the A/C compressor clutch. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 46  Go to Step 42 
36 Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 46  Go to Step 43 
37 Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 46  Go to Step 44 
38 Inspect for poor connections at the harness connector of the powertrain control module (PCM). Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 46  Go to Step 45 
39 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 46  -
40  Replace the evaporator temperature sensor. Refer to Evaporator Core Replacement in Heating, Ventilation and Air Conditioning.
Did you complete the replacement?		 Go to Step 46  -
41 Replace the A/C compressor clutch relay.
Did you complete the replacement?		 Go to Step 46  -
42 Replace the A/C compressor clutch coil. Refer to Compressor Replacement in Heating, Ventilation, and Air Conditioning.
Did you complete the replacement?		 Go to Step 46   
43 Replace the HVAC control module. Refer to HVAC Control Module Replacement (Buick)  or HVAC Control Module Replacement (Pontiac) .
Did you complete the replacement?		 Go to Step 46  -
44 Replace the BCM. Refer to Body Control Module Replacement in Body Control Systems.
Did you complete the replacement?		 Go to Step 46  -
45
IMPORTANT: Program the PCM.
Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement in Engine Controls - 3.4L.Did you complete the replacement?		 Go to Step 46  -
46 Operate the system in order to verify the repair.
Did you correct the condition?		 System OK Go to Step 4 
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