Pinpoint Test Q: The Blower Motor Does Not Operate Correctly
Climate Control System
Pinpoint Tests
Pinpoint Test Q: The Blower Motor Does Not Operate Correctly
Refer to Wiring Diagram Set 54, Manual Climate Control System 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, voltage is provided to the blower motor relay coil and switch contacts. When the blower motor relay coil receives a ground from the HVAC module, the relay coil is energized and voltage is delivered from the blower motor relay to the blower motor and the blower motor speed control. A varying ground for the blower motor is provided from the blower motor speed control. Ground is provided for the blower control module. The HVAC module sends a Pulse Width Modulated (PWM) signal to the blower motor speed control to vary the blower speed.
- DTC B10AF:11 (Blower Fan Relay: Circuit Short to Ground) - The module senses ground on the relay coil ground circuit when the relay is not grounded by the HVAC module, indicating a short directly to ground.
- DTC B10B9:12 (Blower Control: Circuit Short to Battery) - The module senses excessive voltage on the blower motor control PWM circuit, indicating a short directly to voltage.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Blower motor speed control
- HVAC module
PINPOINT TEST Q: THE BLOWER MOTOR DOES NOT OPERATE CORRECTLY
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Q1 CHECK THE HVAC MODULE FOR DTCs
- Ignition ON.
- Check the HVAC module for DTCs.
- Are any DTCs present?
Yes
For DTC B10AF:11, REPAIR circuit CH123 (VT/GN) for a short to ground. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
For DTC B10B9:12, GO to Q4.
No
GO to Q2.
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Q2 VERIFY THE BLOWER MOTOR OPERATION
- Ignition ON.
- Select PANEL on the HVAC module. Adjust the blower motor setting to LO and then to HI then press the POWER button on the HVAC module (OFF).
- Does the blower motor operate at any setting and/or turn OFF?
Yes
If the blower motor operates always in HI, GO to Q3. If the blower motor is always ON, GO to Q5. All other symptoms, INSTALL a new blower motor speed control. REFER to Climate Control Service and Repair. TEST the system for normal operation. If the blower motor still does not operate correctly, GO to Q7.
No
GO to Pinpoint Test P. Pinpoint Test P: The Blower Motor is Inoperative
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Q3 CHECK THE BLOWER MOTOR GROUND CIRCUIT FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: Blower Motor Speed Control C271.
- Ignition ON.
- Does the blower motor operate?
Yes
REPAIR circuit CH218 (GN/VT) for a short to ground. TEST the system for normal operation.
No
INSTALL a new blower motor speed control. REFER to Climate Control Service and Repair. TEST the system for normal operation.
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Q4 CHECK THE BLOWER MOTOR SPEED CONTROL COMMAND CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: Blower Motor Speed Control C271.
- Disconnect: HVAC Module C228.
- Ignition ON.
- Measure the voltage between blower motor speed control C271-5, circuit VH101 (WH/VT), harness side and ground.
- Is any voltage present?
Yes
REPAIR circuit VH101 (WH/VT) for a short to voltage. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
No
INSTALL a new blower motor speed control. REFER to Climate Control Service and Repair. TEST the system for normal operation.
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Q5 CHECK THE BLOWER FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: Blower Motor Relay.
- Disconnect: HVAC Module C228.
- Measure the resistance between blower motor relay socket pin 2, circuit CH123 (VT/GN) and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to Q6.
No
REPAIR circuit CH123 (VT/GN) for a short to ground. TEST the system for normal operation.
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Q6 CHECK THE BLOWER MOTOR RELAY COIL SWITCHED GROUND CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: Blower Motor C2004.
- Ignition ON.
- Measure the voltage between blower motor C2004-2, circuit CH402 (YE/GN), harness side and ground.
- Is any voltage present?
Yes
REPAIR circuit CH402 (YE/GN) for a short to voltage. TEST the system for normal operation.
No
INSTALL a new blower motor speed control. REFER to Climate Control Service and Repair. TEST the system for normal operation. If the blower motor still does not operate correctly, GO to Q7.
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Q7 CHECK THE HVAC MODULE CONNECTION
- Inspect the HVAC 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. CLEAR the DTCs. REPEAT the self-test. TEST the system for normal operation.
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