Pinpoint Test U: The Auxiliary Blower Motor Does Not Operate Correctly
Climate Control System
Pinpoint Test U: The Auxiliary Blower Motor Does Not Operate Correctly
Refer to Wiring Diagram Set 52, Auxiliary Climate Control for schematic and connector information. Diagrams By Number
Refer to Wiring Diagram Set 55, Automatic Climate Control System for schematic and connector information. Diagrams By Number
Normal Operation
Under normal operation, when the Rear Heating Ventilation Air Conditioning (RHVAC) module auxiliary blower motor speed is adjusted, the RHVAC module sends the selected blower motor speed from the RHVAC module over the Medium Speed Controller Area Network (MS-CAN) bus to the HVAC module. When the auxiliary blower motor speed is selected on the Front Display Interface Module (FDIM) touch screen, the FDIM sends the selected blower motor speed from the FDIM over the MS-CAN bus to the HVAC module.
The auxiliary blower motor relay coil receives a ground from the HVAC module. Voltage is supplied to the relay switch contact and coil. When the relay coil is energized, voltage is delivered from the relay to the auxiliary blower motor speed control and auxiliary blower motor. The auxiliary blower motor speed control is grounded. The HVAC module provides a Pulse-Width Modulation (PWM) signal to the auxiliary blower motor speed control to control the blower speed. Ground for the motor is provided through circuit VHA19 (BN) from the auxiliary blower motor speed control.
- DTC B10B0:11 (Rear Blower Fan Relay: Circuit Short to Ground) - The module senses a continuous ground on the relay coil ground circuit when the HVAC module is not grounding the circuit, indicating a short to ground.
- DTC B10BA:14 (Rear Blower Control: Circuit Short to Ground or Open) - The module senses no voltage on the blower motor control PWM circuit, indicating an open or a short to ground.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- HVAC module
- Auxiliary climate control assembly
- Auxiliary blower motor speed control
- Auxiliary blower motor relay
PINPOINT TEST U: THE AUXILIARY BLOWER MOTOR DOES NOT OPERATE CORRECTLY
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U1 CHECK THE HVAC MODULE FOR DTCs
- Ignition ON.
- Check the HVAC module for DTCs.
- Are DTCs present?
Yes
For DTC B10B0:11, REPAIR circuit CH112 (VT/WH) for a short to ground. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
For DTC B10BA:14, REPAIR circuit VHA25 (BN/VT) for a short to ground. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
No
CARRY OUT the auxiliary blower motor relay component test.
Refer to Blower Motor Relay for component testing.
If the relay tests OK, GO to U2.
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U2 CHECK CIRCUIT CHA02 (BN/GN) FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: Auxiliary Blower Motor Speed Control C3002.
- Disconnect: Auxiliary Blower Motor Relay.
- Ignition ON.
- Measure the voltage between ground and auxiliary blower motor speed control C3002-2, circuit CHA02 (BN/GN), harness side.
- Is any voltage present?
Yes
REPAIR circuit CHA02 (BN/GN) for a short to voltage. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
No
GO to U3.
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U3 CHECK CIRCUIT VHA19 (BN) FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: Auxiliary Blower Motor C3021.
- Measure the resistance between ground and auxiliary blower motor C3002-1, circuit VHA19 (BN), harness side.
- Is the resistance greater than 10,000 ohms?
Yes
GO to U4.
No
REPAIR circuit VHA19 (BN) for a short to ground. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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U4 CHECK THE BLOWER MOTOR
- Ignition OFF.
- Connect: Auxiliary Blower Motor C3021.
- Ignition ON.
- Connect a fused jumper lead between auxiliary blower motor speed control C3002-6, circuit GD149 (BK/GY), harness side and C3002-1, circuit VHA19 (BN), harness side.
- Does the blower motor operate at high speed?
Yes
INSTALL a new auxiliary blower motor speed control. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation. If the blower motor still operates incorrectly, GO to U5.
No
INSTALL a new auxiliary blower motor. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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U5 CHECK THE HVAC MODULE CONNECTION
- Inspect the module connectors for:
- corrosion.
- pushed-out terminals.
- damaged terminals.
- Connect and correctly seat all the HVAC module connectors.
- Clear the DTCs.
- Operate the system and verify the concern is still present.
- Is the concern still present?
Yes
INSTALL a new HVAC module. REFER to Climate Control Heating Ventilation Air Conditioning (HVAC) Module. TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
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