For 1990-2009 cars

### 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.

### Diagnostic Fault Information

Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance
--- | --- | --- | --- | ---
Ignition 3 HVAC Relay B+ | 2 | 2 | -- | --
HVAC Control Module B+ | 2 | 2 | -- | --
Blower Motor B+ | 2 | 2 | 2 | --
Blower Motor Control | 1 | 1 | 1 | --
Ignition 3 HVAC Relay Control | 2 | 2 | 2 | --
Low Speed Control | 1 | 1 | 1 | --
Medium 1 Control | 1 | 1 | 1 | --
Medium 2 Control | 1 | 1 | 1 | --
HVAC Relay Ground | -- | 2 | 2 | --
HVAC Control Module Ground | -- | 2 | 2 | --
1. Blower Motor Malfunction 2. Blower Motor Inoperative

### 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 resistor

When the operator requests high speed, the HVAC control module applies ground directly to the blower motor.

When the OFF position is selected, the HVAC control module applies ground to the off input within the HVAC control module through the off blower motor control circuit. When the HVAC control module receives this input, any air conditioning (A/C) requests will be cancelled and the A/C request LED will not be illuminated.

### Reference Information

#### Schematic Reference

HVAC Schematics

#### Connector End View Reference

Component Connector End Views

#### 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

Control Module References for scan tool information

### Circuit/System Verification

Ignition ON, place the blower switch in the Low, Medium 1, Medium 2 and High speed positions. The blower motor should operate in each speed position.

⇒ | If the blower motor is inoperative at all speeds, refer to Blower Motor Inoperative.

⇒ | If the blower motor functions at a single speed only, refer to Blower Motor Malfunction.

### Circuit/System Testing

#### Blower Motor Inoperative

1. Ignition OFF, disconnect the IGN 3 HVAC relay.
2. Ignition ON, verify a test lamp illuminates between the B+ circuit terminal 85 and ground.

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

3. Verify a test lamp illuminates between the B+ circuit terminal 85 and ground.

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

4. Connect a test lamp between the B+ circuit terminal 85 and the control circuit terminal 86.
5. Ignition ON, verify the test lamp illuminates.

⇒ | If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.

6. Ignition OFF, connect the IGN 3 HVAC relay. Disconnect the X1 harness connector at the HVAC control module.
7. Ignition OFF, test for less than 1.0 ohm between the ground circuit terminal 14 and ground.

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

8. Ignition ON, verify a test lamp illuminates between the ignition circuit terminal 8 and ground.

⇒ | If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the IGN 3 HVAC relay.

9. Ignition OFF, connect the X1 harness connector at the HVAC control module. Disconnect the X2 harness connector at the HVAC control module.
10. Test for less than 1.0 ohm between the ground circuit terminal B and ground.

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

11. Ignition OFF, connect the X2 harness connector at the HVAC control module. Disconnect the X1 harness connector at the HVAC control module.
12. Ignition ON, verify a test lamp illuminates between the ignition circuit terminal 8 and ground.

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

13. Ignition OFF, connect the X2 harness connector at the HVAC control module. Disconnect the harness connector at the blower motor.
14. Ignition ON, verify a test lamp illuminates between the ignition circuit terminal 1 and ground.

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

15. Ignition OFF, blower switch HIGH, test for less than 5 ohms between the control circuit terminal 2 and ground.

⇒ | If greater than the specified range, test the control circuit for an open/high resistance. If the circuit tests normal, replace the HVAC control module.

16. If all circuits test normal, test or replace the blower motor.

#### Blower Motor Malfunction

1. Ignition OFF, disconnect the harness connector at the blower motor resistor.
2. Ignition ON, verify that a test lamp illuminates between B+ and the corresponding control circuit terminal listed below while selecting the Low, Medium 1, Medium 2 and High speed positions:

• | Low control terminal D

• | M1 control terminal A

• | M2 control terminal B

• | High control terminal C

⇒ | 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 tests normal, replace the HVAC control module.

3. If all circuits test normal, test or replace the blower motor resistor.

### Component Testing

#### HVAC Relay

1. Ignition OFF, disconnect the HVAC relay.
2. Test for 60-180 ohms between terminals 85 and 86.

⇒ | If the resistance is not within the specified range, replace the relay.

3. Test for infinite resistance between the following terminals:

• | 30 and 86

• | 30 and 87

• | 30 and 85

• | 85 and 87

⇒ | If not the specified value, replace the relay.

4. Install a 30A fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms between terminals 30 and 87.

⇒ | If greater than the specified range, replace the relay.

#### Blower Motor

1. Ignition OFF, disconnect the harness connector at the blower motor.
2. Install a 30A fused jumper wire between the B+ circuit terminal B and 12 volts. Install a jumper wire between the control circuit terminal A and ground. Verify the blower motor activates.

⇒ | If the blower motor does not activate, replace the blower motor.

### Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

• | Blower Motor Replacement

• | Heater and Air Conditioning Control Replacement

• | Blower Motor Resistor Assembly Replacement

• | Underhood Electrical Center or Junction Block Replacement

• | Control Module References for BCM replacement, setup, and programming