Pinpoint Test R: The Blower Motor Does Not Operate Correctly - EATC
Climate Control System
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
The blower motor control module receives a 1-2 volt signal from the HVAC module through circuit 260 (RD/OG) to determine the desired blower motor speed. The HVAC module receives a feedback voltage from the blower motor control module through circuit 752 (YE/RD) to determine actual blower motor speed. When the highest blower motor setting is selected, the HVAC module sends 12 volts to the blower control module through circuit 754 (LG/WH). Ground for the motor is provided through circuit 515 (OG/RD) from the blower control module.
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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