The auxiliary blower motor switchs applies ground to the auxiliary 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 any auxiliary blower switch is in the High speed position, ground is applied directly to the auxiliary blower motor. When the front switch is in the AUX position, the switch supplies ground to the rear auxiliary blower switch.

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Automatic HVAC Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, place the front auxiliary blower switch in each blower speed position. The auxiliary blower motor should operate in all speed positions.

⇒	If the blower motor does not function properly in each speed position, perform the Front Auxiliary Blower Switch Malfunction test.

2. Ignition ON, place the front auxiliary blower switch in the AUX position. Place the rear auxiliary blower switch in each speed position. The auxiliary blower motor should operate in all speed positions.

⇒	If the blower motor does not function properly in each speed position, perform the Rear Auxiliary Blower Switch Malfunction test.

Front Auxiliary Blower Switch Malfunction

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

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

3. Connect the harness connector at the front auxiliary blower motor switch. Disconnect the harness connector at the auxiliary blower motor resistor.
4. 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 4

•	M1 control terminal 2

•	M2 control terminal 3

•	High control terminal 1

⇒	If the test lamp does not illuminate, test the appropriate control circuit for an open/high resistance. If the circuit tests normal, replace the front auxiliary blower motor switch.

⇒	If the test lamp is always illuminated, test the appropriate control circuit for a short to ground. If the circuit tests normal, replace the front auxiliary blower motor switch.

5. Ignition OFF, connect the harness connector at the auxiliary blower motor resistor. Disconnect the harness connector at the auxiliary blower motor.
6. Place the front auxiliary blower motor switch in the Off position. Verify that a test lamp does not illuminate between B+ and the control circuit terminal 1.

⇒	If the test lamp illuminates, test the control circuits for a short to ground.

7. Ignition ON, place the front auxiliary blower motor switch in the Low speed position. Verify that a test lamp illuminates between B+ and the control circuit terminal 1.

⇒	If the test lamp does not illuminate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the auxiliary blower motor resistor.

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

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

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

Rear Auxiliary Blower Switch Malfunction

1. Ignition OFF, disconnect the harness connector at the rear auxiliary blower motor switch. Place the front auxiliary blower motor switch in the AUX position.
2. Test for less than 1.0 ohm between the ground circuit terminal C 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 front auxiliary blower motor switch.

3. Connect the harness connector at the rear auxiliary blower motor switch. Disconnect the harness connector at the auxiliary blower motor resistor.
4. 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 4

•	M1 control terminal 2

•	M2 control terminal 3

•	High control terminal 1

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

⇒	If the test lamp is always illuminated, test the appropriate control circuit for a short to ground.

5. If all circuits tests normal, replace the rear auxiliary blower motor switch.

Auxiliary Blower Motor

1. Ignition OFF, disconnect the harness at the blower motor.
2. Install a 40-amp fused jumper wire between circuit terminal 1 and 12 volts. Install a jumper wire between the low reference circuit terminal 2 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.