Pinpoint Test S: The Blower Motor Does Not Operate Correctly
Climate Control System
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 and switch contact receive. The coil receives ground from the HVAC module if any position but OFF is selected. When the relay coil is energized, voltage is delivered to the blower motor from the relay. Ground for the motor is provided from the blower motor speed control. Ground is provided for the blower motor speed control.
The blower motor speed control receives a 1-2 volt signal from the HVAC module to determine the desired blower motor speed. The HVAC module receives a feedback voltage from the blower motor speed control 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.
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 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 Service and Repair. 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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