Pinpoint Test R: The Blower Motor Does Not Operate Correctly - EATC
Climate Control System
Pinpoint Tests
Pinpoint Test R: The Blower Motor Does Not Operate Correctly - EATC
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 control module
- HVAC module
PINPOINT TEST R: THE BLOWER MOTOR DOES NOT OPERATE CORRECTLY - EATC
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R1 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.
- 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 R2.
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R2 CHECK THE BLOWER MOTOR SPEED CONTROL
- Ignition OFF.
- Connect: Blower Motor Speed Control C1308.
- Disconnect: HVAC Module C228B.
- Ignition ON.
- Does the blower motor operate?
Yes
INSTALL a new blower motor speed control. TEST the system for normal operation.
No
GO to R3.
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R3 CHECK THE BLOWER MOTOR SPEED CONTROL CIRCUITS FOR AN OPEN
- Ignition OFF.
- Disconnect: Blower Motor Speed Control C1308.
- Measure the resistance between the blower motor speed control, harness side and Electronic Automatic Temperature Control (EATC), harness side using the following chart.
- Are the resistances less than 5 ohms?
Yes
GO to R4.
No
REPAIR the affected circuit for an open. TEST the system for normal operation.
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R4 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 R5.
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R5 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 R6.
No
REPAIR the affected circuit for a short to ground. TEST the system for normal operation.
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R6 CHECK THE BLOWER MOTOR SPEED CONTROL CIRCUITS FOR SHORTS
- Measure the resistance between blower motor speed control:
- C1308-2, circuit 752 (YE/RD), harness side and C1308-3, circuit 754 (LG/WH), harness side.
- C1308-2, circuit 752 (YE/RD), harness side and C1308-1, circuit 260 (RD/OG), harness side.
- C1308-3, circuit 754 (LG/WH), harness side and C1308-1, circuit 260 (RD/OG), harness side.
- Are the resistances greater than 10,000 ohms?
Yes
GO to R7.
No
REPAIR the affected circuits. TEST the system for normal operation.
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R7 CHECK THE HVAC MODULE HIGH BLOWER OUTPUT
- Connect: HVAC Module C228B.
- Connect: Blower Motor Speed Control C1308.
- Ignition ON.
- Adjust the blower motor speed to HI.
- Measure the voltage between HVAC module C228B-24, circuit 754 (LG/WH), harness side and ground by back-probing the HVAC module C228B.
- Is the voltage within 2 volts of battery voltage?
Yes
GO to R8.
No
INSTALL a new HVAC module. TEST the system for normal operation.
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R8 CHECK THE HVAC MODULE BLOWER CONTROL OUTPUT
- Adjust the blower motor speed to LO.
- Measure the voltage between HVAC module C228B-23, circuit 752 (YE/RD), harness side and ground by back-probing the HVAC module C228B.
- Is the voltage greater than 1 volt?
Yes
INSTALL a new blower motor speed control. TEST the system for normal operation.
No
INSTALL a new HVAC module. TEST the system for normal operation.
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