The blower motor switch 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:

When the operator requests high speed, the blower motor switch applies ground directly to the blower motor.

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, mode selector set to Vent, replace the blower motor switch in each speed position, the blower motor should activate and operate from low to high when changing between the commanded states.

Blower Motor Inoperative

1. Ignition OFF, disconnect the harness connector at the blower motor switch.
2. Ignition OFF, test for less than 1.0 ohm between the ground circuit terminal 1 and ground.

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

3. Ignition OFF, connect the harness connector at the blower motor switch and disconnect the BLOWER MOTOR relay.
4. Test for less than 1.0 ohm between the relay coil ground circuit terminal and ground.

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

5. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal and ground.

⇒	If the test lamp illuminates, test the control circuit for a short to voltage.

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

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

8. Ignition OFF, connect the BLOWER MOTOR relay and disconnect the harness connector at the blower motor.
9. Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal B and ground.

⇒	If the test lamp is always OFF, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the BLOWER MOTOR relay.

10. Connect a test lamp between the control circuit terminal A and B+.
11. Command the blower motor ON and OFF by moving the blower motor speed control switch from the OFF to the 4 speed position. The test lamp should turn ON and OFF when changing between the commanded states.

⇒	If the test lamp is always ON, test the control circuit for a short to ground, if the circuit tests normal, replace the blower motor switch.

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

12. 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 assembly.
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:

•	1 speed control terminal 3

•	2 speed control terminal 2

•	3 speed control terminal 4

⇒	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 blower motor switch.

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

Relay

1. Ignition OFF, disconnect the BLOWER MOTOR 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 30-amp 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 30-amp fused jumper wire between the relay controlled output circuit terminal A and 12 volts. Install a jumper wire between the control circuit terminal B and ground. Verify the blower motor activates.

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

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.