Pinpoint Test S: the Blower Motor Does Not Operate Correctly
Climate Control System
Pinpoint Tests
Pinpoint Test S: The Blower Motor Does Not Operate Correctly
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 voltage through circuit 181 (BN/OG). The coil receives ground from the HVAC module through circuit 364 (BK/LG) if any position but OFF is selected. Voltage is supplied to the relay switch contact through circuit 181 (BN/OG). When the relay coil is energized, voltage is delivered to the blower motor through circuit 371 (PK/WH). Ground for the motor is provided through circuit 515 (OG/RD) from the blower motor speed control. Ground for the blower motor speed control is provided by circuit 57 (BK).
The blower motor speed control receives a 1-2 volt signal from the HVAC module through circuit 752 (YE/RD) to determine the desired blower motor speed. The HVAC module receives a feedback voltage from the blower motor speed control through circuit 260 (RD/OG) to determine actual blower motor speed. When the highest blower motor setting is selected, the HVAC module sends 12 volts to the blower motor speed control through circuit 754 (LG/WH).
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Blower motor speed control
- HVAC module
PINPOINT TEST S: THE BLOWER MOTOR DOES NOT OPERATE CORRECTLY
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S1 CHECK CIRCUIT 515 (OG/RD) FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: Blower Motor Speed Control C1308.
- Ignition ON.
- Press the panel button on the HVAC module. Adjust the blower motor setting to LO and then to HI.
- Does the blower motor operate?
Yes
REPAIR circuit 515 (OG/RD) for a short to ground. TEST the system for normal operation.
No
GO to S2.
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S2 CHECK THE BLOWER MOTOR SPEED CONTROL
- Ignition OFF.
- Connect: Blower Motor Speed Control C1308.
- Disconnect: HVAC Module C228a.
- Disconnect: Blower Motor Relay.
- Connect a fused jumper wire between blower motor relay socket pin 30, circuit 181 (BN/OG) and pin 87, circuit 371 (PK/WH).
- Ignition ON.
- Does the blower motor operate?
Yes
INSTALL a new blower motor speed control. TEST the system for normal operation.
No
GO to S3.
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S3 CHECK THE BLOWER MOTOR SPEED CONTROL CIRCUITS FOR AN OPEN
- Ignition OFF.
- Disconnect: Blower Motor Speed Control C1308.
- Measure the resistance between blower motor speed control C1308-1, circuit 260 (RD/OG), harness side and HVAC module C228a-3, circuit 260 (RD/OG), harness side.
- Measure the resistance between blower motor speed control C1308-2, circuit 752 (YE/RD), harness side and HVAC module C228a-16, circuit 752 (YE/RD), harness side.
- Measure the resistance between blower motor speed control C1308-3, circuit 754 (LG/WH), harness side and HVAC module C228a-8, circuit 754 (LG/WH), harness side.
- Are the resistances less than 5 ohms?
Yes
GO to S4.
No
REPAIR the affected circuit for an open. TEST the system for normal operation.
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S4 CHECK THE BLOWER MOTOR SPEED CONTROL CIRCUITS FOR A SHORT TO VOLTAGE
- Ignition ON.
- Measure the voltage between blower motor speed control:
- C1308-1, circuit 260 (RD/OG), harness side and ground.
- C1308-2, circuit 752 (YE/RD), harness side and ground.
- C1308-3, circuit 754 (LG/WH), harness side and ground.
- Is any voltage present?
Yes
REPAIR the affected circuit for a short to voltage. TEST the system for normal operation.
No
GO to S5.
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S5 CHECK THE BLOWER MOTOR SPEED CONTROL CIRCUITS FOR A SHORT TO GROUND
- Ignition OFF.
- Measure the resistance between blower motor speed control:
- C1308-1, circuit 260 (RD/OG), harness side and ground.
- C1308-2, circuit 752 (YE/RD), harness side and ground.
- C1308-3, circuit 754 (LG/WH), harness side and ground.
- Are the resistances greater than 10,000 ohms?
Yes
GO to S6.
No
REPAIR the affected circuit for a short to ground. TEST the system for normal operation.
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S6 CHECK THE BLOWER MOTOR SPEED CONTROL CIRCUITS FOR SHORTS
- Measure the resistance between blower motor speed control:
- C1308-1, circuit 260 (RD/OG), harness side and C1308-2, circuit 752 (YE/RD), harness side.
- C1308-1, circuit 260 (RD/OG), harness side and C1308-3, circuit 754 (LG/WH), harness side.
- C1308-2, circuit 752 (YE/RD), harness side and C1308-3, circuit 754 (LG/WH), harness side.
- Are the resistances greater than 10,000 ohms?
Yes
GO to S7.
No
REPAIR the affected circuits for a short together. TEST the system for normal operation.
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S7 CHECK THE HVAC MODULE HIGH BLOWER OUTPUT
- Connect: HVAC C228a.
- Connect: Blower Motor Speed Control C1308.
- Ignition ON.
- Adjust the blower motor speed to HI.
- Measure the voltage between HVAC module C228a-8, circuit 754 (LG/WH), harness side and ground by back-probing the HVAC module C228a.
- Is the voltage within 2 volts of battery voltage?
Yes
GO to S8.
No
GO to S9.
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S8 CHECK THE HVAC MODULE BLOWER CONTROL OUTPUT
- Adjust the blower motor speed to LO.
- Measure the voltage between HVAC module C228a-16, circuit 752 (YE/RD), harness side and ground by back-probing the HVAC module C228a.
- Is the voltage greater than one volt?
Yes
INSTALL a new blower motor speed control. TEST the system for normal operation.
No
GO to S9.
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S9 CHECK HVAC MODULE CONNECTION
- Carry out the HVAC Module Cold Boot Process. HVAC Module Cold Boot Process
- Carry out the HVAC Module On-Demand Self Test. HVAC Module Self-Test
- Operate the system.
- Does the concern return?
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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