Hummer H3. Manual — part 1294

8

Test the A/C request signal circuit of the
body control module (BCM) for a short to
voltage. Refer to Circuit Testing and
Wiring Repairs .
Did you find and correct the condition?

Go to Step 17

Go to Step 12

9

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 17

Go to Step 13

10

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 17

Go to Step 14

11

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 17

Go to Step 15

12

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 17

Go to Step 16

13

Replace the A/C compressor clutch relay.
Refer to Compressor Relay
Replacement .
Did you complete the replacement?

Go to Step 17

-

14

Replace the A/C compressor. Refer to
Compressor Replacement .
Did you complete the replacement?

Go to Step 17

-

15

Replace the HVAC control module. Refer
to Heater and Air Conditioning
Control Replacement.
Did you complete the replacement?

Go to Step 17

-

2007 Hummer H3

2007 HVAC HVAC - Manual - H3

AIR CONDITIONING COMPRESSOR MALFUNCTION

Diagnostic Instructions

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

Review Strategy Based Diagnosis for an overview of the diagnostic approach.

Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Circuit/System Description

When the A/C switch is pressed, the HVAC control assembly grounds the A/C request signal
circuit. The body control module (BCM) receives the ground input and sends a GMLAN message
to the engine control module (ECM) for an A/C request. This input will request the ECM to
ground the A/C compressor clutch relay control circuit, which will switch the A/C CLUTCH
relay. With the relay contacts closed, battery voltage is supplied to the A/C compressor clutch
assembly.

Diagnostic Aids

The following conditions must be met in order for the ECM to turn on the compressor clutch:

Battery voltage is between 9-16 volts.

Engine coolant temperature (ECT) is less than 123°C (253°F).

Engine speed is less than 5300 RPM.

Engine speed is more than 600 RPM.

A/C high side pressure is between 2951-310 kPa (428-44 psi).

Throttle position is less than 100 percent.

Evaporator temperature is greater than 0°C (32°F).

ECM does not detect excessive torque load.

ECM does not detect insufficient idle quality.

16

Replace the BCM. Refer to Control
Module References for replacement,
setup and programming.
Did you complete the replacement?

Go to Step 17

-

17

Operate the system in order to verify the
repair.
Did you correct the condition?

System OK

Go to Step 3

2007 Hummer H3

2007 HVAC HVAC - Manual - H3

Reference Information

Schematic Reference

HVAC Schematics

Electrical Information Reference

Circuit Testing

Connector Repairs

Testing for Intermittent Conditions and Poor Connections

Wiring Repairs

Scan Tool Reference

Scan Tool Output Controls

Scan Tool Data List

Scan Tool Data Definitions

Circuit/System Verification

1. Press the A/C request switch. The A/C compressor clutch should engage.

2. Place the mode switch in the defrost position. The A/C compressor clutch should engage.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector C2 at the HVAC control module.

2. Ignition OFF, test for less than 1.0 ohm of resistance between the ground circuit terminal L

and ground.

If greater than 1.0 ohm, test the ground circuit for an open/high resistance.

3. Ignition ON, install a 3-amp fused jumper wire between the signal circuit terminal G and

ground. Verify the scan tool A/C Request Switch parameter is ON.

If not On, test the signal circuit for a short to voltage or an open/high resistance. If
circuit tests normal, replace the BCM.

4. Connect the harness connector C2 at the HVAC control module. With a scan tool, verify the

A/C Request Switch parameter cycles between On and Off with each press of the A/C
switch.

If the parameter does not cycle, test the signal circuit for a short to ground. If the
circuit tests normal, replace the HVAC control module.

2007 Hummer H3

2007 HVAC HVAC - Manual - H3

5. Disconnect the A/C compressor clutch relay.

6. Verify that a test lamp illuminates between the relay coil B+ circuit and ground.

If the test lamp does not illuminate, test the B+ circuit for a short to ground or an
open/high resistance.

7. Verify that a test lamp illuminates between the relay switch B+ circuit and ground.

If the test lamp does not illuminate, test the relay switch B+ circuit for an open/high
resistance. If the A/C fuse is open, test the relay switch control circuit for a short to
ground. If all circuits test normal, test or replace the A/C compressor clutch.

8. Disconnect the harness connector at the A/C compressor clutch.

9. Ignition OFF, test for less than 1.0 ohm of resistance between the A/C compressor ground

circuit and ground.

If greater than 1.0 ohm, test the ground circuit for an open/high resistance.

10. Connect the harness connector at the A/C compressor clutch.

11. Ignition ON, connect a 10-amp fused jumper wire between the relay switch B+ circuit and

the relay switch control circuit. Verify the A/C compressor clutch engages.

If the A/C compressor clutch does not activate, test the control circuit for an open/high
resistance. If the circuit tests normal, test or replace the A/C compressor.

12. Connect a test lamp between the relay control circuit and the relay coil B+ circuit.

13. Using a scan tool, command the A/C relay output ON and OFF. The test lamp should turn

ON and OFF when changing between the commanded states.

If the test lamp remains ON at all times, test for a short to ground on the control
circuit. If the circuit tests normal, replace the ECM.

If the test lamp remains OFF at all times, test for a short to voltage or an open/high
resistance on the control circuit. If the circuit tests normal, replace the ECM.

14. If all circuits test normal, test or replace the A/C CLTCH relay.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Compressor Replacement

Control Module References for BCM, HVAC and ECM replacement, setup and
programming

BLOWER MOTOR MALFUNCTION

Diagnostic Instructions

2007 Hummer H3

2007 HVAC HVAC - Manual - H3