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Home >> Hummer >> 2008 >> H2 4D Utility Wagon >> Repair and Diagnosis >> External Pages >> Different car >> Section 127 (HVAC System - Automatic) >> Diagnostic Information and Procedures >> HVAC Compressor Clutch Does Not Disengage >> Test Description

Test Description

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The number below refers to the step number on the diagnostic table.

  1. 2:  These actions will disable the HVAC control module output to powertrain control module (PCM) or engine control module (ECM).
HVAC Compressor Clutch Does Not Disengage

Step Action Yes No
Schematic Reference: HVAC Schematics 
Connector End View Reference: HVAC Connector End Views 
DEFINITION: The A/C compressor clutch will not disengage when an A/C request has not 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 mode switch in the PANEL position.
  3. Place the A/C request switch in the OFF position.
Does the A/C compressor clutch engage?		 Go to Step 3  Go to Testing for Intermittent Conditions and Poor Connections
3
  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.
Does the test lamp illuminate?		 Go to Step 4  Go to Step 8 
4 Test the supply voltage circuit of the A/C compressor clutch for a short to voltage. Refer to Circuit Testing and Wiring Repairs .
Did you find and correct the condition?		 Go to Step 13  Go to Step 5 
5
  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp between the control circuit and the ignition 3 voltage circuit of the A/C compressor clutch relay.
Does the test lamp illuminate?		 Go to Step 6  Go to Step 7 
6 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 13  Go to Step 9 
7 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 13  Go to Step 10 
8 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 13  Go to Step 11 
9 Inspect for poor connections at the harness connector of the powertrain control module (PCM) or engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs .
Did you find and correct the condition?		 Go to Step 13  Go to Step 12 
10 Replace the A/C compressor clutch relay.
Did you complete the replacement?		 Go to Step 13  -
11 Replace the A/C compressor. Refer to Compressor Replacement .
Did you complete the replacement?		 Go to Step 13  -
12 Replace the PCM/ECM. Refer to Control Module References for replacement, setup, and programming.
Did you complete the replacement?		 Go to Step 13  -
13 Operate the system in order to verify the repair.
Did you correct the condition?		 System OK Go to Step 3 
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