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HVAC Compressor Clutch Does Not Engage

WARNING: This page is about a different car, the 2007 Cadillac DTS. However, it is still accessible from the selected car via links, so may be relevant.
HVAC Compressor Clutch Does Not Engage

Step Action Values 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 Diagnostic System Check - Vehicle? - Go to Step 2  Go to Diagnostic System Check - Vehicle
2
  1. Start the engine.
  2. Place the blower motor switch in the maximum speed position.
  3. Ensure the A/C OFF switch is not selected.
  4. Place the left air temperature switch in the coldest position.
Does the A/C compressor operate?		 - Go to Testing for Intermittent Conditions and Poor Connections Go to Step 3 
3
  1. Start the engine.
  2. Observe the coolant temperature indicator.
Is the engine coolant temperature indicator illuminated?		   Go to Diagnostic System Check - Vehicle Go to Step 4 
4
  1. Turn OFF the ignition.
  2. Install the ACR 2000.
  3. Record the ambient temperature at the vehicle.
  4. Record readings of the low and high side STATIC pressures.
  5. Compare the low and the high side pressure values with the allowable limits for the recorded ambient air temperature.
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 5  Go to Leak Testing
5
  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool observe the A/C refrigerant pressure sensor in the engine control module (ECM) data list.
  4. Compare the A/C refrigerant pressure sensor parameter on the scan tool with the ACR 2000 high side pressure value.
Is the scan tool A/C refrigerant pressure sensor parameter and the ACR 2000 pressure value within 15 psi of each other?		 - Go to Step 6  Go to Step 14 
6 With a scan tool, view the evaporator temperature in the HVAC system data.
Is the evaporator temperature below 4°C (39°F)?		 - Go to Step 17  Go to Step 7 
7 With a scan tool, view the ambient air temperature in the HVAC system data.
Is the ambient air temperature below 3°C (38°F)?		 - Go to Step 18  Go to Step 8 
8
  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the supply voltage circuit of the A/C compressor clutch with a test lamp that is connected to ground.
  5. With a scan tool, command the A/C compressor clutch relay ON.
Does the test lamp illuminate?		 - Go to Step 9  Go to Step 10 
9 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 .
Did you find and correct the condition?		 - Go to Step 29  Go to Step 13 
10 Test the voltage supply circuit of the A/C compressor clutch for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 29  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 battery positive voltage circuit of the A/C compressor clutch relay with a test lamp that is connected to ground.
Does the test lamp illuminate?		 - Go to Step 12  Go to Step 25 
12 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 29  Go to Step 26 
13 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 29  Go to Step 27 
14
  1. Disconnect the A/C pressure sensor.
  2. With a test lamp connected to battery voltage, probe the ground circuit at the A/C pressure sensor connector.
Does the test lamp illuminate?		 - Go to Step 19  Go to Step 15 
15 Test the ground circuit of the A/C refrigerant pressure sensor for a high resistance or for an open. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 29  Go to Step 16 
16 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 29  Go to Step 28 
17 Inspect the evaporator temperature sensor circuits for high resistance. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 - Go to Step 29  Go to Step 21 
18 Inspect the outside air temperature sensor circuits for high resistance. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		   Go to Step 29  Go to Step 22 
19 Inspect for poor connections at the harness connector of the A/C pressure sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?		   Go to Step 29  Go to Step 20 
20 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 29  -
21 Inspect for poor connections at the harness connector of the evaporator temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?		 - Go to Step 29  Go to Step 23 
22 Inspect for poor connections at the harness connector of the ambient air temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?		   Go to Step 29  Go to Step 24 
23 Replace the evaporator temperature sensor. Refer to Evaporator Core Replacement .
Did you complete the replacement?		 - Go to Step 29  -
24 Replace the ambient air temperature sensor. Refer to Ambient Air Temperature Sensor Replacement .
Did you complete the replacement?		   Go to Step 29  -
25 Repair the battery positive voltage circuit of the A/C compressor clutch relay. Refer to Wiring Repairs .
Did you complete the repair?		 - Go to Step 29  -
26 Replace the A/C compressor clutch relay.
Did you complete the replacement?		 - Go to Step 29  -
27 Replace the A/C compressor clutch. Refer to Compressor Replacement .
Did you complete the replacement?		 - Go to Step 29  -
28 Replace the HVAC control module. Refer to Control Module References for replacement, setup and programming.
Did you complete the replacement?		 - Go to Step 29  -
29 Operate the system in order to verify the repair.
Did you correct the condition?		 - System OK Go to Step 2 
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