Pinpoint Test T: The Blower Motor Does Not Operate Correctly - DATC
Climate Control System
Pinpoint Tests
Pinpoint Test T: The Blower Motor Does Not Operate Correctly - DATC
Refer to Wiring Diagram Set 55, Automatic Climate Control System for schematic and connector information. Diagrams By Number
Normal Operation
Under normal operation, the blower motor relay coil receives a ground from the HVAC module - Dual Automatic Temperature Control (DATC). The blower motor relay coil is provided voltage. Voltage is supplied to the blower motor relay switch contact. When the blower motor relay blower motor relay coil is grounded by the DATC, the blower motor relay is energized an voltage is delivered to the blower motor control module. Ground for the blower motor speed control is provided. The HVAC module - DATC provides a blower target speed signal to the blower motor speed control. This is used to control the blower speed. The actual blower speed signal is provided to the HVAC module - DATC from the blower motor speed control. Ground for the motor is provided from the blower motor speed control.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Blower motor speed control
- Blower motor relay
- HVAC module - DATC
PINPOINT TEST T: THE BLOWER MOTOR DOES NOT OPERATE CORRECTLY - DATC
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T1 VERIFY THE BLOWER MOTOR OPERATION
- Ignition ON.
- Press the panel button on the HVAC module - DATC. Adjust the blower motor setting to LO and then to HI.
- Does the blower motor operate at any setting?
Yes
GO to T2.
No
Go To Pinpoint Test S. Pinpoint Test S: The Blower Motor Is Inoperative - DATC
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T2 CHECK THE BLOWER MOTOR SPEED TARGET POSITION (BLWR_T#) HVAC PID
- Enter the following diagnostic mode on the scan tool: BLWR_T# HVAC PID.
- Observe the BLWR_T# HVAC PID while increasing and decreasing the blower speed.
- Does the BLWR_T# HVAC PID reading change in all speeds between 0% and 100%?
Yes
If the blower motor is always on, CARRY OUT the blower motor relay component test.
If the relay tests OK, GO to T7.
All other symptoms, GO to T3.
No
GO to T9.
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T3 CHECK CIRCUITS (BU), VH101 (WH/VT)/(RD) AND CH102 (YE/BU)/(BN) FOR A SHORT TO VOLTAGE
- Disconnect: HVAC Module - DATC C228A.
- Disconnect: Blower Motor Speed Control C271.
- Disconnect: Blower Motor C288.
- Ignition ON.
- Measure the voltage between ground and:
- blower motor speed control C271-1, circuit (RD), harness side.
- blower motor speed control C271-3, circuit (BN), harness side.
- blower motor speed control C271-5, circuit (BU), harness side.
- Is any voltage present?
Yes
REPAIR circuit VH101 (WH/VT)/(RD), CH102 (YE/BU)/(BN) or (BU) for a short to voltage. TEST the system for normal operation.
No
GO to T4.
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T4 CHECK CIRCUITS (BU) AND CH102 (YE/BU)/(BN) FOR A SHORT TO GROUND
- Ignition OFF.
- Measure the resistance between ground and:
- blower motor speed control C271-5, circuit (BU), harness side.
- blower motor speed control C271-3, circuit (BN), harness side.
- Are the resistances greater than 10,000 ohms?
Yes
GO to T5.
No
REPAIR circuit (BU) or CH102 (YE/BU)/(BN) for a short to ground. TEST the system for normal operation.
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T5 CHECK CIRCUITS VH101 (WH/VT)/(RD) AND CH102 (YE/BU)/(BN) FOR A SHORT TOGETHER
- Measure the resistance between blower motor speed control C271-1, circuit (RD), harness side and blower motor speed control C271-3, circuit (BN), harness side.
- Is the resistance greater than 10,000 ohms?
Yes
GO to T6.
No
REPAIR circuit VH101 (WH/VT)/(RD) or CH102 (YE/BU)/(BN) for a short together. TEST the system for normal operation.
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T6 CHECK CIRCUIT CH102 (YE/BU)/(BN) FOR AN OPEN
- Measure the resistance between blower motor speed control C271-3, circuit (BN), harness side and HVAC module - DATC C228B-15, circuit CH102 (YE/BU), harness side.
- Are the resistances less than 5 ohms?
Yes
INSTALL a new blower motor speed control. TEST the system for normal operation. If the condition returns, INSTALL a new HVAC module - DATC. TEST the system for normal operation.
No
REPAIR circuit CH102 (YE/BU)/(BN) for an open. TEST the system for normal operation.
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T7 CHECK CIRCUIT CH402 (YE/GN)/(BK) FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: Blower Motor Relay.
- Disconnect: Blower Motor C288.
- Ignition ON.
- Measure the voltage between ground and blower motor C288-2, circuit (BK), harness side.
- Is any voltage present?
Yes
REPAIR circuit CH402 (YE/GN)/(BK) for a short to voltage. TEST the system for normal operation.
No
GO to T8.
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T8 CHECK CIRCUIT CH123 (VT/GN) FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: HVAC Module - DATC C228A.
- Measure the resistance between ground and blower motor relay socket, circuit CH123 (VT/GN) and ground.
- Is the resistance greater than 10,000 ohms?
Yes
GO to T9.
No
REPAIR circuit CH123 (VT/GN) for a short to ground. TEST the system for normal operation.
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T9 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. 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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