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
--- | --- | --- | --- | ---
HVAC Control Assembly Ignition | 1 | 1 | -- | --
Blower Motor Control | 1 | 1 | 2 | --
Low Speed Control | 1 | 1 | 2 | --
Medium 1 Speed Control | 1 | 1 | 2 | --
Medium 2 Speed Control | 1 | 1 | 2 | --
High Speed Control | 1 | 1 | 2 | --
Blower Motor Resistor Assembly Ground | -- | 1 | 1 | --
Blower Motor Ground | -- | 1 | -- | --
1. Blower Motor Inoperative 2. Blower Motor Always On

### Circuit/System Description

The HVAC control assembly applies voltage 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

• | High speed- 0 resistors

### Reference Information

#### Schematic Reference

HVAC Schematics

#### Connector End View Reference

Component Connector End Views

#### Description and Operation

• | Air Delivery Description and Operation

• | Air Temperature Description and Operation

#### Electrical Information Reference

• | Circuit Testing

• | Connector Repairs

• | Testing for Intermittent Conditions and Poor Connections

• | Wiring Repairs

### Circuit/System Verification

Ignition ON, mode selector set to Panel, cycle the blower motor from LOW to HIGH using the blower motor switch. The blower motor should operate in each speed position.

### Circuit/System Testing

1. Ignition OFF, disconnect the X 1 harness connector at the HVAC control assembly.
2. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal 13 and ground.

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

3. Ignition OFF, connect the X2 harness connector at the HVAC control assembly. Connect the X1 harness connector at the HVAC control assembly.
4. Ignition ON, cycle the mode selector through each position. Verify a test lamp illuminates between the control circuit terminal A in each mode position.

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

5. Ignition OFF, connect the X1 harness connector at the HVAC control assembly. Disconnect the harness connector at the blower motor resistor assembly.
6. Test for less than 5 ohms between the ground circuit terminal 3 and ground.

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

7. Ignition ON, verify a test lamp illuminates between the B+ circuit terminal 7 and ground.

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

8. Mode selector set to Panel, while changing the fan speed switch between LOW, M1, M2 and HIGH, verify that a test lamp illuminates between the appropriate control circuit terminals listed below and ground:

• | LOW - terminal 4

• | M1 - terminal 1

• | M2 - terminal 2

• | HIGH - terminal 5

⇒ | 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 assembly.

9. Ignition OFF, connect the harness connector at the blower motor resistor assembly. Disconnect the harness connector at the blower motor.
10. Test for less than 5 ohms between the ground circuit terminal 7 and ground.

⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. If the circuit tests normal, replace the blower motor resistor assembly.

11. Ignition ON, mode selector set to Panel, connect a test lamp between the control circuit terminal 6 and ground circuit terminal 7.
12. Cycle the fan speed switch between LOW, M1, M2 and HIGH speeds. The test lamp should illuminate and change in intensity as the blower speed is varied.

⇒ | If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the blower motor resistor assembly.

⇒ | If the test lamp illuminates but does not change intensity, test the control circuit for a short to voltage. If the circuit tests normal, replace the blower motor resistor assembly.

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

### Component Testing

1. Ignition OFF, disconnect the harness connector at the blower motor.
2. Install a 40-amp fused jumper wire between the control circuit terminal 6 and 12 volts. Install a jumper wire between the ground circuit terminal 7 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 Resistor Assembly Replacement

• | Blower Motor Replacement

• | Heater and Air Conditioning Control Replacement