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For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2001 🢒 Firebird 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 HVAC Compressor Clutch Does Not Engage

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. The A/C compressor relay output is disabled if engine coolant temperature is above 121°C (250°F) for the L36 and 125°C (257°F) for the LS1.

  1. 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.

  2. The HVAC control assembly 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.

Step

Action

Values

Yes

No

Schematic Reference: HVAC Schematics

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 review the HVAC operation and perform the necessary inspections?

 

Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Manual

2

  1. Install a scan tool.
  2. Start the engine.
  3. With a scan tool, observe the coolant temperature sensor (ECT) parameter in the Powertrain data list.

Does the scan tool indicate that the ECT parameter is above the specified temperature?

3.8 L (L36) 121°C (250°F)

5.7 L (LS1) 125°C (257°F)

Go to Engine Overheating in Engine Cooling

Go to Step 3

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, the allow the A/C system to equalize for approximately 2 minutes.
  4. Ensure that the ignition key is in the OFF position.
  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 .

Are the pressure values within specifications for the 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 A/C high side pressure on the scan tool to the high side pressure value on the ACR2000.

Are the high side pressure values with 103 kpa (15 psi) of each other?

 

Go to Step 6

Go to Step 17

6

Is the HVAC control assembly inoperative?

 

Go to Step 16

Go to Step 7

7
  1. Start the engine.
  2. With a scan tool, observe the A/C request parameter in the Powertrain data list.
  3. Place the air temperature switch in the coldest position.
  4. Turn the blower motor to the on position.
  5. Place the A/C request switch in the ON position.

Does the scan tool indicate that the A/C request parameter is YES?

 

Go to Step 10

Go to Step 8

8

Does the A/C request indicator illuminate?

 

Go to Step 9

Go to Step 28

9
  1. Turn OFF the ignition.
  2. Test the A/C request signal circuit 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 35

Go to Step 29

10

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 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 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 12

Go to Step 23

12
  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 24

Go to Step 13

13

Does the test lamp remain illuminated with each command?

 

Go to Step 20

Go to Step 19

14
  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 15

Go to Step 24

15
  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 26

Go to Step 21

16

Test the voltage supply circuits to the HVAC control assembly 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 35

Go to Step 18

17

Test the ground circuit of the A/C 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 35

Go to Step 25

18

Test the ground circuit of the HVAC control assembly for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

 

Go to Step 35

Go to Step 28

19

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 35

Go to Step 29

20

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 35

Go to Step 29

21

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 35

Go to Step 22

22

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 35

Go to Step 27

23

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 35

--

24

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 35

--

25

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 in Wiring Systems.

Did you find and correct the condition?

 

Go to Step 35

Go to Step 30

26

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 35

Go to Step 31

27

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 32

28

Inspect for poor connections at the harness connector of the HVAC control assembly. 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 35

Go to Step 33

29

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 35

Go to Step 34

30

Replace the A/C high pressure switch. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement in Heating, Ventilation, and Air Conditioning.

Did you complete the replacement?

 

Go to Step 35

--

31

Replace the A/C compressor clutch relay.

Did you complete the replacement?

 

Go to Step 35

--

32

Replace the A/C compressor clutch coil. Refer to Compressor Clutch Plate and Hub Assembly Removal and Compressor Clutch Plate/Hub Assembly Install in Heating, Ventilation, and Air Conditioning.

Did you complete the replacement?

 

Go to Step 35

--

33

Replace the HVAC control assembly. Refer to Heater and Air Conditioning Control Replacement .

Did you complete the replacement?

 

Go to Step 35

--

34

Important:  Perform the reprogramming procedure for the PCM.

Replace the PCM. Refer to one of the following procedures:

    •  Powertrain Control Module Replacement in Engine Controls-3.8L
    •  Powertrain Control Module Replacement in Engine Controls-5.7L

Did you complete the replacement?

 

Go to Step 35

--

35

Operate the system in order to verify the repair.

Did you correct the condition?

 

System OK

Go to Step 4