Pinpoint Test Q: The Blower Motor Is Inoperative - EATC
Climate Control System
Pinpoint Test Q: The Blower Motor is Inoperative - 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 receives ground through circuit 57 (BK). The coil receives voltage through circuit 1812 (BN/WH). Voltage is supplied to the relay switch contact through circuit 364 (BK/LG). 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 control module. Ground for the blower control module is provided by circuit 57 (BK).
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).
This pinpoint test is intended to diagnose the following:
- Fuse(s)
- Wiring, terminals or connectors
- Blower motor
- Blower motor relay
- Blower motor control module
- HVAC module
PINPOINT TEST Q: THE BLOWER MOTOR IS INOPERATIVE - EATC
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Q1 VERIFY THE BLOWER MOTOR OPERATION
- Ignition ON.
- Press the PANEL button on the HVAC module. Adjust the blower motor setting to LO and then to HI.
- Is the blower motor inoperative in all settings?
Yes
GO to Q2.
No
Go To Pinpoint Test R. Pinpoint Test R: The Blower Motor Does Not Operate Correctly - EATC
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Q2 CHECK FOR VOLTAGE TO THE BLOWER MOTOR
- Ignition OFF.
- Disconnect: Blower Motor C1227.
- Ignition ON.
- Measure the voltage between blower motor C1227-1, circuit 371 (PK/WH), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to Q3.
No
GO to Q8.
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Q3 CHECK THE BLOWER MOTOR
- Ignition OFF.
- Connect: Blower Motor C1227.
- Disconnect: Blower Motor Speed Control C1308.
- Connect a fused jumper lead between blower motor speed control C1308-4, circuit 515 (OG/RD), harness side and C1308-5, circuit 57 (BK), harness side.
- Ignition ON.
- Does the blower motor operate?
Yes
GO to Q6.
No
GO to Q4.
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Q4 CHECK CIRCUIT 57 (BK) FOR AN OPEN
- Ignition OFF.
- Remove the fused jumper lead from blower motor speed control C1308.
- Measure the resistance between blower motor speed control C1308-5, circuit 57 (BK), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to Q5.
No
REPAIR circuit 57 (BK) for an open. TEST the system for normal operation.
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Q5 CHECK CIRCUIT 515 (OG/RD) FOR AN OPEN
- Disconnect: Blower Motor C1227.
- Measure the resistance between blower motor C1227-2, circuit 515 (OG/RD), harness side and blower motor speed control C1308-4, circuit 515 (OG/RD), harness side.
- Is the resistance less than 5 ohms?
Yes
INSTALL a new blower motor. TEST the system for normal operation.
No
REPAIR circuit 515 (OG/RD) for an open. TEST the system for normal operation.
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Q6 CHECK THE HVAC MODULE OUTPUT
- Ignition OFF.
- Remove the fused jumper lead from the blower motor speed control C1308.
- 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 Q7.
No
INSTALL a new HVAC module. TEST the system for normal operation.
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Q7 CHECK CIRCUIT 754 (LG/WH) FOR AN OPEN OR SHORT TO GROUND
- Ignition OFF.
- Disconnect: Blower Motor Speed Control C1308.
- Disconnect: HVAC Module C228b.
- Measure the resistance between:
- HVAC module C228b-24, circuit 754 (LG/WH), harness side and blower motor speed control C1308-3, circuit 754 (LG/WH), harness side.
- HVAC module C228b-24, circuit 754 (LG/WH), harness side and ground.
- Is the resistance less than 5 ohms between the HVAC module and the blower motor speed control and greater than 10,000 ohms between the HVAC module and ground?
Yes
INSTALL a new blower motor speed control. TEST the system for normal operation.
No
REPAIR circuit 754 (LG/WH) for an open or short to ground. TEST the system for normal operation.
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Q8 CHECK CIRCUIT 371 (PK/WH) FOR AN OPEN
- Ignition OFF.
- Disconnect: Blower Motor Relay.
- Measure the resistance between blower motor relay socket pin 87, circuit 371 (PK/WH) and blower motor C1227-1, circuit 371 (PK/WH), harness side.
- Is the resistance less than 5 ohms?
Yes
GO to Q9.
No
REPAIR circuit 371 (PK/WH) for an open. TEST the system for normal operation.
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Q9 CHECK CIRCUIT 364 (BK/LG) FOR AN OPEN
- Measure the voltage between blower motor relay socket pin 30, circuit 364 (BK/LG) and ground.
- Is the voltage 10 volts or greater?
Yes
GO to Q10.
No
VERIFY the Battery Junction Box (BJB) fuse 101 (40A) is OK. If OK, REPAIR circuit 364 (BK/LG) for an open. TEST the system for normal operation.
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Q10 CHECK THE BLOWER MOTOR RELAY
NOTICE: The following step uses a test light to simulate normal circuit loads. Use only the test lamp recommended in the Special Tools table at the beginning or equivalent. To avoid connector terminal damage, use the Rotunda Flex Probe Kit for the test light probe connection to the vehicle. Do not use the test lamp probe directly on any connector.
- Ignition ON.
- Connect a 12-volt test light between blower motor relay socket pin 86, circuit 1812 (BN/WH) and blower motor relay socket pin 85, circuit 57 (BK).
- Does the test light illuminate?
Yes
INSTALL a new blower motor relay. TEST the system for normal operation.
No
GO to Q11.
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Q11 CHECK CIRCUIT 1812 (BN/WH) FOR AN OPEN
- Measure the voltage between blower motor relay socket pin 86, circuit 1812 (BN/WH) and ground.
- Is the voltage 10 volts or greater?
Yes
REPAIR circuit 57 (BK) for an open. TEST the system for normal operation.
No
VERIFY the Central Junction Box (CJB) fuse 15 (10A) is OK. If OK, REPAIR circuit 1812 (BN/WH) for an open. TEST the system for normal operation.
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