Hummer H3. Manual — part 1295

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

The HVAC control assembly applies a ground to the blower motor control circuit that
corresponds to the selected blower speed. The resistors and the blower motor are in a series
circuit. The following list represents the number of resistors in series with the blower motor per
particular speed request:

Low speed, 3 resistors

Medium 1 speed, 2 resistors

Medium 2 speed, 1 resistors

When the operator requests High speed, the HVAC control assembly applies ground to the high
speed blower relay control circuit. When the relay contacts close, ground is applied directly to
the blower motor through the blower motor resistor.

Reference Information

Schematic Reference

HVAC Schematics

Description and Operation

Air Temperature Description and Operation

Air Delivery Description and Operation

Electrical Information Reference

Circuit Testing

Connector Repairs

Testing for Intermittent Conditions and Poor Connections

Wiring Repairs

Scan Tool Reference

2007 Hummer H3

2007 HVAC HVAC - Manual - H3

Scan Tool Output Controls

Scan Tool Data List

Scan Tool Data Definitions

Circuit/System Verification

1. Turn ON the ignition, verify that the HVAC relay turns on.

If the HVAC relay does not turn on, refer to the HVAC Relay Malfunction test under
Circuit/System Testing.

2. Ignition On, place the blower switch in the highest speed position, the blower motor should

operate at High speed.

If the blower motor does not function properly in the High speed position, refer to
High Speed Blower Malfunction under Circuit/System Testing.

3. Place the blower switch in Low, Medium 1 and Medium 2 speed positions. The blower

motor should operate in each speed position.

If the blower motor does not function properly in each speed position, refer to Blower
Malfunction under Circuit/System Testing.

Circuit/System Testing

HVAC Relay Malfunction

1. Ignition OFF, disconnect the HVAC relay in the underhood fuse block.

2. Test for less than 1.0 ohm of resistance between the relay coil ground circuit terminal and

ground.

If greater than specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify that a test lamp illuminates between the relay coil control circuit

terminal and ground.

If the test lamp does not illuminate, replace the underhood fuse block.

4. If all circuits test normal, test or replace the HVAC relay.

High Speed Blower Malfunction

1. Ignition OFF, disconnect the harness connector C1 at the HVAC Control Module.

2. Ignition OFF, test for less than 1.0 ohm of resistance between the ground circuit terminal 5

and ground.

If greater than the specified range, test the ground circuit for an open/high resistance.

2007 Hummer H3

2007 HVAC HVAC - Manual - H3

3. Connect the harness connector at the HVAC Control Module.

4. Disconnect the High Speed Blower Relay.

5. Place the blower switch in the high speed position.

6. Ignition OFF test for less than 1.0 ohm of resistance between the ground circuit terminal 5

and ground.

If greater than the specified range, test the ground circuit for an open/high resistance.
If the circuit test normal test or replace the HVAC Control Module.

7. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 2 and

ground.

If the test lamp does not illuminate, test the ignition circuit for an open/high resistance.

8. Test for less than 1.0 ohm of resistance between the ground circuit terminal 1 and ground.

If greater than the specified range, test the ground circuit for an open/high resistance.

9. Connect the High Speed Blower Relay. Disconnect the harness connector at the Blower

Motor Resistor.

10. Ignition ON, place the blower switch in the high speed position.

11. Test for less than 1.0 ohm of resistance between the control circuit terminal E at the Blower

Motor resistor and ground.

If greater than the specified range, test the control circuit for an open/high resistance.
If the circuit test normal test or replace the High Speed Blower Relay.

12. Ignition OFF, connect the harness connector at the Blower Motor Resistor. Connect the

High Speed Blower Relay. Disconnect the harness connector at the Blower Motor.

13. Ignition On, place the blower switch in the high speed position.

14. Verify that a test lamp illuminates between the control circuit terminal 1 and B+.

If the test lamp does not illuminate, test the control circuit for an open/high resistance.

If the circuit test normal, test or replace the Blower Motor Resistor.

15. Verify that a test lamp illuminates between the ignition circuit terminal 2 and ground.

If the test lamp does not illuminate test the ignition circuit for an open/high resistance.

16. If all circuits test normal, test or replace the Blower Motor.

Blower Malfunction

1. Ignition OFF, disconnect the harness connector at the HVAC Control Module.

2. Test for less than 1.0 ohm of resistance between the ground circuit terminal 5 and ground.

If greater than the specified range, test the ground circuit for an open/high resistance.

3. Connect the harness connector at the HVAC Control Module.

2007 Hummer H3

2007 HVAC HVAC - Manual - H3

4. Disconnect the harness connector at the Blower Motor Resistor.

5. Ignition ON, place the Blower Switch in the appropriate speed for the circuit being tested.

6. Verify that a test lamp illuminates between the appropriate control circuit and B+.

If the test lamp does not illuminate, test the appropriate control circuit for a short to
ground or an open/high resistance. If the circuit test normal, test or replace the HVAC
control Module.

7. If all circuits test normal, test or replace the Blower Motor Resistor.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References

Blower Motor Replacement (Left Hand Drive) or Blower Motor Replacement (Right
Hand Drive)

Heater and Air Conditioning Control Replacement

Blower Motor Resistor Assembly Replacement (Left Hand Drive) or Blower Motor
Resistor Assembly Replacement (Right Hand Drive)

TOO HOT IN VEHICLE

Test Description

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

4: The HVAC control module is inoperative when the module does not respond to an
operator control request.

5: If the condition does not occur when an A/C request has been made, then you must bypass
the A/C performance test procedures.

6: These actions are the enable criteria for the A/C compressor to operate. Ambient air
temperature must be above 3°C (38°F) in order for this A/C compressor test to be run.

7: Performing the Air Conditioning System Performance Test ensures that the A/C system is
operating properly for further testing.

9: If no condition is found with all conditions listed, then compare door travel to a known
good vehicle.

Too Hot in Vehicle

Step

Action

Values

Yes

No

2007 Hummer H3

2007 HVAC HVAC - Manual - H3