Auxiliary Blower Motor Malfunction RPO C36
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 |
|---|---|---|---|---|
Low Speed Auxiliary Blower Motor Relay Switch B+ | 1 | 1 | -- | -- |
Medium Speed Auxiliary Blower Motor Relay Switch B+ | 1 | 1 | -- | -- |
High Speed Auxiliary Blower Motor Relay Switch B+ | 1 | 1 | -- | -- |
Low Speed Auxiliary Blower Motor Relay Coil Ignition | 1 | 1 | -- | -- |
Medium Speed Auxiliary Blower Motor Relay Coil Ignition | 1 | 1 | -- | -- |
High Speed Auxiliary Blower Motor Relay Coil Ignition | 1 | 1 | -- | -- |
Low Speed Auxiliary Blower Motor Relay Coil Control | 2 | 5 | 2 | -- |
Medium Speed Auxiliary Blower Motor Relay Coil Control | 3 | 5 | 3 | -- |
High Speed Auxiliary Blower Motor Relay Coil Control | 4 | 5 | 4 | -- |
Low Speed Auxiliary Blower Motor Relay Switch Output Control | 5 | 2 | 1 | -- |
Medium Speed Auxiliary Blower Motor Relay Switch Output Control | 5 | 3 | 1 | -- |
High Speed Auxiliary Blower Motor Relay Switch Output Control | 5 | 4 | 1 | -- |
Auxiliary Blower Motor Control | 5 | 1 | 1 | -- |
Auxiliary Blower Motor Ground | -- | 1 | -- | -- |
Auxiliary Blower Motor Switch Ground | -- | 1 | -- | -- |
1. Auxiliary Blower Motor Inoperative - All Speeds 2. Auxiliary Blower Motor Inoperative - Low 3. Auxiliary Blower Motor Inoperative - Medium 4. Auxiliary Blower Motor Inoperative - High 5. Auxiliary Blower Motor Always ON | ||||
Circuit/System Description
The auxiliary blower motor switch applies a ground to the appropriate auxiliary blower motor relay 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, 2 resistors |
| • | Medium speed, 1 resistor |
When high fan speed has been selected, the blower motor switch applies a ground to the coil side of auxiliary high speed blower motor relay which energizes the relay and provides B+ voltage to the auxiliary blower motor.
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Ignition ON, cycle the auxiliary blower between the LOW, MED and HIGH speed positions. The blower motor should operate at the appropriate speed in each position.
| ⇒ | If the blower motor is inoperative at all speeds, refer to Blower Motor Inoperative. |
| ⇒ | If the blower motor is inoperative in only one speed or does not change speed when cycling between the speed positions, refer to Blower Motor Malfunction. |
Circuit/System Testing
Blower Motor Inoperative
- Ignition OFF, disconnect the harness connector at the auxiliary blower motor switch.
- Ignition OFF, test for less than 5 ohms between the ground circuit terminal B and ground.
- Ignition OFF, connect the harness connector at the auxiliary blower motor switch. Disconnect the auxiliary high speed blower motor relay.
- Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal C2 and ground.
- Verify that a test lamp illuminates between the B+ circuit terminal C1 and ground.
- Ignition OFF, disconnect the harness connector at the auxiliary blower motor.
- Test for less than 5 ohms between the ground circuit terminal A and ground.
- Connect the harness connector at the auxiliary blower motor.
- Ignition ON, connect a 30A fused jumper wire between the B+ circuit terminal C1 and the control circuit terminal A2. Verify the auxiliary blower motor turn ON.
- If all circuits test normal, test or replace the auxiliary blower motor switch.
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | 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 and the ignition circuit fuse is open, test the relay coil ignition circuit at each of the auxiliary blower motor relays for a short to ground. If the circuits test normal, replace the appropriate relay. |
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the relay switch B+ circuit at each of the auxiliary blower motor relays as well as the relay switch output control circuits for a short to ground. |
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If the auxiliary blower motor does not turn ON, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the auxiliary blower motor. |
Blower Motor Malfunction
- Ignition OFF, disconnect the appropriate blower motor relay.
- Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal A2 and ground.
- Verify that a test lamp illuminates between the ignition circuit terminal C2 and ground.
- Verify that a test lamp illuminates between the B+ circuit terminal C1 and ground.
- Connect a 30A fused jumper wire between the B+ circuit terminal C1 and the control circuit terminal A2. Verify the auxiliary blower motor turn ON.
- Connect a test lamp between the ignition circuit terminal C2 and the control circuit terminal A1.
- Cycle the auxiliary blower motor switch between OFF and the appropriate speed position. The test lamp should turn ON and OFF when changing between the commanded states.
- If all circuits test normal, test or replace the appropriate auxiliary blower motor relay.
| ⇒ | If the test lamp illuminates, test the control circuit for a short to voltage. |
| ⇒ | If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. |
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. |
| ⇒ | If the auxiliary blower motor does not turn ON, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the auxiliary blower motor resistor assembly. |
| ⇒ | If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the auxiliary 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 auxiliary blower motor switch. |
Component Testing
Relay
- Ignition OFF, disconnect the appropriate blower motor relay.
- Test for 60-180 ohms between terminals 85 and 86.
- Test for infinite resistance between the following terminals:
- 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 the resistance is not within the specified range, replace the relay. |
| • | 30 and 86 |
| • | 30 and 87 |
| • | 30 and 85 |
| • | 85 and 87 |
| ⇒ | If not the specified value, replace the relay. |
| ⇒ | If greater than the specified range, replace the relay. |
Blower Motor
- Ignition OFF, disconnect the harness connector at the auxiliary blower motor.
- Install a 30-amp fused jumper wire between the control circuit terminal B and 12 volts. Install a jumper wire between the ground circuit terminal A and ground. Verify the auxiliary blower motor activates.
| ⇒ | If the blower motor does not activate, replace the auxiliary blower motor. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Auxiliary Blower Motor Malfunction RPO C69 w/o Rear Controls
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 |
|---|---|---|---|---|
Low Speed Auxiliary Blower Motor Relay Switch B+ | 1 | 1 | -- | -- |
Medium Speed Auxiliary Blower Motor Relay Switch B+ | 1 | 1 | -- | -- |
High Speed Auxiliary Blower Motor Relay Switch B+ | 1 | 1 | -- | -- |
Low Speed Auxiliary Blower Motor Relay Coil Ignition | 1 | 1 | -- | -- |
Medium Speed Auxiliary Blower Motor Relay Coil Ignition | 1 | 1 | -- | -- |
High Speed Auxiliary Blower Motor Relay Coil Ignition | 1 | 1 | -- | -- |
Low Speed Auxiliary Blower Motor Relay Coil Control | 2 | 5 | 2 | -- |
Medium Speed Auxiliary Blower Motor Relay Coil Control | 3 | 5 | 3 | -- |
High Speed Auxiliary Blower Motor Relay Coil Control | 4 | 5 | 4 | -- |
Low Speed Auxiliary Blower Motor Relay Switch Output Control | 5 | 2 | 1 | -- |
Medium Speed Auxiliary Blower Motor Relay Switch Output Control | 5 | 3 | 1 | -- |
High Speed Auxiliary Blower Motor Relay Switch Output Control | 5 | 4 | 1 | -- |
Auxiliary Blower Motor Control | 5 | 1 | 1 | -- |
Auxiliary Blower Motor Ground | -- | 1 | -- | -- |
Auxiliary Blower Motor Switch Ground | -- | 1 | -- | -- |
1. Auxiliary Blower Motor Inoperative - All Speeds 2. Auxiliary Blower Motor Inoperative - Low 3. Auxiliary Blower Motor Inoperative - Medium 4. Auxiliary Blower Motor Inoperative - High 5. Auxiliary Blower Motor Always ON | ||||
Circuit/System Description
The front auxiliary HVAC control assembly applies a ground to the appropriate auxiliary blower motor relay 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, 2 resistors |
| • | Medium speed, 1 resistor |
When high fan speed has been selected, the blower motor switch applies a ground to the coil side of auxiliary high speed blower motor relay which energizes the relay and provides B+ voltage to the auxiliary blower motor.
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Ignition ON, cycle the front auxiliary HVAC control assembly blower switch between the LOW, MED and HIGH speed positions. The blower motor should operate at the appropriate speed in each position.
| ⇒ | If the blower motor is inoperative at all speeds, refer to Blower Motor Inoperative. |
| ⇒ | If the blower motor is inoperative in only one speed or does not change speed when cycling between the speed positions, refer to Blower Motor Malfunction. |
Circuit/System Testing
Blower Motor Inoperative
- Ignition OFF, disconnect the harness connector at the front auxiliary HVAC control assembly.
- Ignition OFF, test for less than 5 ohms between the ground circuit terminal F and ground.
- Ignition OFF, connect the harness connector at the front auxiliary HVAC control assembly. Disconnect the auxiliary high speed blower motor relay.
- Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal C2 and ground.
- Verify that a test lamp illuminates between the B+ circuit terminal C1 and ground.
- Ignition OFF, disconnect the harness connector at the auxiliary blower motor.
- Test for less than 5 ohms between the ground circuit terminal A and ground.
- Connect the harness connector at the auxiliary blower motor.
- Ignition ON, connect a 30A fused jumper wire between the B+ circuit terminal C1 and the control circuit terminal A2. Verify the auxiliary blower motor turn ON.
- If all circuits test normal, test or replace the front auxiliary HVAC control assembly.
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | 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 and the ignition circuit fuse is open, test the relay coil ignition circuit at each of the auxiliary blower motor relays for a short to ground. If the circuits test normal, replace the appropriate relay. |
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the relay switch B+ circuit at each of the auxiliary blower motor relays as well as the relay switch output control circuits for a short to ground. |
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If the auxiliary blower motor does not turn ON, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the auxiliary blower motor. |
Blower Motor Malfunction
- Ignition OFF, disconnect the appropriate blower motor relay.
- Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal A2 and ground.
- Verify that a test lamp illuminates between the ignition circuit terminal C2 and ground.
- Verify that a test lamp illuminates between the B+ circuit terminal C1 and ground.
- Connect a 30A fused jumper wire between the B+ circuit terminal C1 and the control circuit terminal A2. Verify the auxiliary blower motor turn ON.
- Connect a test lamp between the ignition circuit terminal C2 and the control circuit terminal A1.
- Cycle the front auxiliary HVAC control assembly blower motor switch between OFF and the appropriate speed position. The test lamp should turn ON and OFF when changing between the commanded states.
- If all circuits test normal, test or replace the appropriate auxiliary blower motor relay.
| ⇒ | If the test lamp illuminates, test the control circuit for a short to voltage. |
| ⇒ | If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. |
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. |
| ⇒ | If the auxiliary blower motor does not turn ON, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the auxiliary blower motor resistor assembly. |
| ⇒ | If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the front auxiliary HVAC control assembly. |
| ⇒ | 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 front auxiliary HVAC control assembly. |
Component Testing
Relay
- Ignition OFF, disconnect the appropriate blower motor relay.
- Test for 60-180 ohms between terminals 85 and 86.
- Test for infinite resistance between the following terminals:
- 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 the resistance is not within the specified range, replace the relay. |
| • | 30 and 86 |
| • | 30 and 87 |
| • | 30 and 85 |
| • | 85 and 87 |
| ⇒ | If not the specified value, replace the relay. |
| ⇒ | If greater than the specified range, replace the relay. |
Blower Motor
- Ignition OFF, disconnect the harness connector at the auxiliary blower motor.
- Install a 30-amp fused jumper wire between the control circuit terminal B and 12 volts. Install a jumper wire between the ground circuit terminal A and ground. Verify the auxiliary blower motor activates.
| ⇒ | If the blower motor does not activate, replace the auxiliary blower motor. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Auxiliary Blower Motor Malfunction RPO C69 with Rear Controls
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 |
|---|---|---|---|---|
Low Speed Auxiliary Blower Motor Relay Switch B+ | 1 | 1 | -- | -- |
Medium Speed Auxiliary Blower Motor Relay Switch B+ | 1 | 1 | -- | -- |
High Speed Auxiliary Blower Motor Relay Switch B+ | 1 | 1 | -- | -- |
Low Speed Auxiliary Blower Motor Relay Coil Ignition | 1 | 1 | -- | -- |
Medium Speed Auxiliary Blower Motor Relay Coil Ignition | 1 | 1 | -- | -- |
High Speed Auxiliary Blower Motor Relay Coil Ignition | 1 | 1 | -- | -- |
Low Speed Auxiliary Blower Motor Relay Coil Control | 2 | 5 | 2 | -- |
Medium Speed Auxiliary Blower Motor Relay Coil Control | 3 | 5 | 3 | -- |
High Speed Auxiliary Blower Motor Relay Coil Control | 4 | 5 | 4 | -- |
Low Speed Auxiliary Blower Motor Relay Switch Output Control | 5 | 2 | 1 | -- |
Medium Speed Auxiliary Blower Motor Relay Switch Output Control | 5 | 3 | 1 | -- |
High Speed Auxiliary Blower Motor Relay Switch Output Control | 5 | 4 | 1 | -- |
Auxiliary Blower Motor Control | 5 | 1 | 1 | -- |
Auxiliary Blower Motor Ground | -- | 1 | -- | -- |
Auxiliary HVAC Control Assembly Ground | -- | 1 | -- | -- |
Front Auxiliary HVAC Control Assembly Ground | -- | 1 | -- | -- |
1. Auxiliary Blower Motor Inoperative - All Speeds 2. Auxiliary Blower Motor Inoperative - Low 3. Auxiliary Blower Motor Inoperative - Medium 4. Auxiliary Blower Motor Inoperative - High 5. Auxiliary Blower Motor Always ON | ||||
Circuit/System Description
The auxiliary blower motor is able to be controlled either by the front auxiliary HVAC control assembly or the rear auxiliary HVAC control assembly. This is accomplished through the auxiliary HVAC control assembly. With the front HVAC control assembly blower switch is in the LOW, MED, or HIGH positions, the front auxiliary HVAC control assembly retains full control of the auxiliary HVAC blower motor by directly applying a ground to the blower motor switch. When the front HVAC control assembly blower switch is in the LOW, MED, or HIGH position, the rear HVAC control assembly inputs are ignored by the auxiliary HVAC control assembly.
When the front auxiliary HVAC control assembly blower switch is placed in the AUX position, control of the system is given to the rear HVAC control assembly. When the front auxiliary HVAC control assembly blower switch is placed in the AUX position, the signal circuit between the front auxiliary HVAC control assembly and the auxiliary HVAC control assembly is grounded, indicating that control should be given to the rear auxiliary HVAC control assembly.
The front auxiliary HVAC control assembly or auxiliary HVAC control assembly applies a ground to the appropriate auxiliary blower motor relay 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, 2 resistors |
| • | Medium speed, 1 resistor |
When high fan speed has been selected, the blower motor switch applies a ground to the coil side of auxiliary high speed blower motor relay which energizes the relay and provides B+ voltage to the auxiliary blower motor.
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Ignition ON, cycle the front auxiliary HVAC control assembly blower switch between the LOW, MED and HIGH speed positions. The blower motor should operate at the appropriate speed in each position.
- Place the front auxiliary HVAC control assembly blower switch in the AUX position.
- Cycle the rear auxiliary HVAC control assembly blower switch between the LOW, MED and HIGH speed positions. The blower motor should operate at the appropriate speed in each position.
| ⇒ | If the blower motor is inoperative at all speeds, refer to Blower Motor Inoperative - Front Control. |
| ⇒ | If the blower motor is inoperative in only one speed or does not change speed when cycling between the speed positions, refer to Blower Motor Malfunction - Front Control. |
| ⇒ | If the blower motor is inoperative at all speeds, refer to Blower Motor Inoperative - Rear Control. |
| ⇒ | If the blower motor is inoperative in only one speed or does not change speed when cycling between the speed positions, refer to Blower Motor Malfunction - Rear Control. |
Circuit/System Testing
Blower Motor Inoperative - Front Control
- Ignition OFF, disconnect the harness connector at the front auxiliary HVAC control assembly.
- Ignition OFF, test for less than 5 ohms between the ground circuit terminal B and ground.
- Connect the harness connector at the front auxiliary HVAC control assembly. Disconnect the harness connector at the auxiliary HVAC control assembly.
- Front auxiliary HVAC control assembly blower switch in the LOW position, test for infinite resistance between the signal circuit terminal M and ground.
- Ignition OFF, connect the harness connector at the auxiliary HVAC control assembly. Disconnect the auxiliary high speed blower motor relay.
- Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal C2 and ground.
- Verify that a test lamp illuminates between the B+ circuit terminal C1 and ground.
- Ignition OFF, disconnect the harness connector at the auxiliary blower motor.
- Test for less than 5 ohms between the ground circuit terminal A and ground.
- Connect the harness connector at the auxiliary blower motor.
- Ignition ON, connect a 30A fused jumper wire between the B+ circuit terminal C1 and the control circuit terminal A2. Verify the auxiliary blower motor turns ON.
- If all circuits test normal, test or replace the front auxiliary HVAC control assembly.
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If less than the specified value, test the signal circuit for a short to ground. If the circuit tests normal, replace the front auxiliary HVAC control assembly. |
| ⇒ | 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 and the ignition circuit fuse is open, test the relay coil ignition circuit at each of the auxiliary blower motor relays for a short to ground. If the circuits test normal, replace the appropriate relay. |
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the relay switch B+ circuit at each of the auxiliary blower motor relays as well as the relay switch output control circuits for a short to ground. |
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If the auxiliary blower motor does not turn ON, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the auxiliary blower motor. |
Blower Motor Malfunction - Front Control
- Ignition OFF, disconnect the appropriate blower motor relay.
- Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal A2 and ground.
- Verify that a test lamp illuminates between the ignition circuit terminal C2 and ground.
- Verify that a test lamp illuminates between the B+ circuit terminal C1 and ground.
- Connect a 30A fused jumper wire between the B+ circuit terminal C1 and the control circuit terminal A2. Verify the auxiliary blower motor turn ON.
- Connect a test lamp between the ignition circuit terminal C2 and the control circuit terminal A1.
- Cycle the front auxiliary HVAC control assembly blower motor switch between OFF and the appropriate speed position. The test lamp should turn ON and OFF when changing between the commanded states.
- If all circuits test normal, test or replace the appropriate auxiliary blower motor relay.
| ⇒ | If the test lamp illuminates, test the control circuit for a short to voltage. |
| ⇒ | If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. |
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. |
| ⇒ | If the auxiliary blower motor does not turn ON, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the auxiliary blower motor resistor assembly. |
| ⇒ | If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the front auxiliary HVAC control assembly. |
| ⇒ | 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 front auxiliary HVAC control assembly. |
Blower Motor Inoperative - Rear Control
- Ignition OFF, disconnect the harness connector at the auxiliary HVAC control assembly.
- Test for less than 5 ohms between the ground circuit terminal H and ground.
- Ignition ON, verify a test lamp illuminates between the ignition circuit terminal J and ground.
- Front auxiliary HVAC control assembly blower switch in the AUX position, test for less than 5 ohms between the signal circuit terminal M and ground.
- Ignition OFF, connect the harness connector at the auxiliary HVAC control assembly. Disconnect the rear auxiliary HVAC control assembly.
- Ignition ON, front auxiliary HVAC control assembly blower switch in the AUX position, test for less than 5 ohms between the control circuit terminal F and ground.
- Ignition OFF, connect the harness connector at the rear auxiliary HVAC control assembly. Disconnect the auxiliary high speed blower motor relay.
- Ignition ON, verify that a test lamp illuminates between the ignition circuit terminal C2 and ground.
- Verify that a test lamp illuminates between the B+ circuit terminal C1 and ground.
- Ignition OFF, disconnect the harness connector at the auxiliary blower motor.
- Test for less than 5 ohms between the ground circuit terminal A and ground.
- Connect the harness connector at the auxiliary blower motor.
- Ignition ON, connect a 30A fused jumper wire between the B+ circuit terminal C1 and the control circuit terminal A2. Verify the auxiliary blower motor turns ON.
- If all circuits test normal, test or replace the rear auxiliary HVAC control assembly.
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. |
| ⇒ | If greater than the specified value, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the front auxiliary HVAC control assembly. |
| ⇒ | If greater than the specified range, test the control circuit for an open/high resistance. If the circuit tests normal, replace the auxiliary HVAC control assembly. |
| ⇒ | 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 and the ignition circuit fuse is open, test the relay coil ignition circuit at each of the auxiliary blower motor relays for a short to ground. If the circuits test normal, replace the appropriate relay. |
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the relay switch B+ circuit at each of the auxiliary blower motor relays as well as the relay switch output control circuits for a short to ground. |
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If the auxiliary blower motor does not turn ON, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the auxiliary blower motor. |
Blower Motor Malfunction - Rear Control
- Ignition OFF, disconnect the appropriate blower motor relay.
- Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal A2 and ground.
- Verify that a test lamp illuminates between the ignition circuit terminal C2 and ground.
- Verify that a test lamp illuminates between the B+ circuit terminal C1 and ground.
- Connect a 30A fused jumper wire between the B+ circuit terminal C1 and the control circuit terminal A2. Verify the auxiliary blower motor turn ON.
- Connect a test lamp between the ignition circuit terminal C2 and the control circuit terminal A1.
- Front auxiliary HVAC control assembly blower switch in the AUX position, cycle the rear auxiliary HVAC control assembly blower motor switch between OFF and the appropriate speed position. The test lamp should turn ON and OFF when changing between the commanded states.
- If all circuits test normal, test or replace the appropriate auxiliary blower motor relay.
| ⇒ | If the test lamp illuminates, test the control circuit for a short to voltage. |
| ⇒ | If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. |
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. |
| ⇒ | If the auxiliary blower motor does not turn ON, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the auxiliary blower motor resistor assembly. |
| ⇒ | If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the rear auxiliary HVAC control assembly. |
| ⇒ | 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 rear auxiliary HVAC control assembly. |
Component Testing
Relay
- Ignition OFF, disconnect the appropriate blower motor relay.
- Test for 60-180 ohms between terminals 85 and 86.
- Test for infinite resistance between the following terminals:
- 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 the resistance is not within the specified range, replace the relay. |
| • | 30 and 86 |
| • | 30 and 87 |
| • | 30 and 85 |
| • | 85 and 87 |
| ⇒ | If not the specified value, replace the relay. |
| ⇒ | If greater than the specified range, replace the relay. |
Blower Motor
- Ignition OFF, disconnect the harness connector at the auxiliary blower motor.
- Install a 30-amp fused jumper wire between the control circuit terminal B and 12 volts. Install a jumper wire between the ground circuit terminal A and ground. Verify the auxiliary blower motor activates.
| ⇒ | If the blower motor does not activate, replace the auxiliary blower motor. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
