Pinpoint Test S: The Blower Motor Does Not Operate Correctly - DATC System
Climate Control System
Pinpoint Tests
Pinpoint Test S: The Blower Motor Does Not Operate Correctly - DATC System
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 control module receives a 1-2 volt signal from the HVAC module - Dual Automatic Temperature Control (DATC) through circuit CH218 (GN/VT) to determine the desired blower motor speed. The HVAC module - DATC receives a feedback voltage from the blower motor control module through circuit VH219 (GY) to determine actual blower motor speed. When the highest blower motor setting is selected, the HVAC module - DATC sends 12 volts to the blower control module through circuit CH217 (BN).
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Blower motor control module
- HVAC module - DATC
PINPOINT TEST S: THE BLOWER MOTOR DOES NOT OPERATE CORRECTLY - DATC SYSTEM
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S1 CHECK CIRCUIT VH301 (YE/BU) FOR A SHORT TO GROUND
- Ignition OFF.
- Disconnect: Blower Motor Speed Control C271.
- Ignition ON.
- Press the PANEL button on the HVAC module - DATC. Adjust the blower motor setting to LO and then to HI.
- Does the blower motor operate?
Yes
REPAIR circuit VH301 (YE/BU) 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 C271.
- Disconnect: HVAC Module - DATC C228a.
- Disconnect: HVAC Module - DATC C228b.
- Disconnect: Blower Motor Relay.
- Connect a fused jumper lead between blower motor relay socket pin 3, circuit SBB16 (VT/RD) and pin 5, circuit CH402 (YE/GN).
- Does the blower motor operate?
Yes
INSTALL a new blower motor speed control module. 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.
- Connect: Blower Motor Relay.
- Disconnect: Blower Motor Speed Control C271.
- Measure the resistance between blower motor speed control C271-1, circuit VH219 (GY), harness side and HVAC module - DATC C228a-5, circuit VH219 (GY), harness side.
- Measure the resistance between blower motor speed control C271-2, circuit CH218 (GN/VT), harness side and HVAC module - DATC C228a-15, circuit CH218 (GN/VT), harness side.
- Measure the resistance between blower motor speed control C271-3, circuit CH217 (BN), harness side and HVAC module - DATC C228b-4, circuit CH217 (BN), 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 ground and blower motor speed control:
- C271-1, circuit VH219 (GY), harness side.
- C271-2, circuit CH218 (GN/VT), harness side.
- C271-3, circuit CH217 (BN), harness side.
- 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 ground and blower motor speed control:
- C271-1, circuit VH219 (GY), harness side.
- C271-2, circuit CH218 (GN/VT), harness side.
- C271-3, circuit CH217 (BN), harness side.
- 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 TOGETHER
- Measure the resistance between blower motor speed control:
- C271-1, circuit VH219 (GY), harness side and C271-2, circuit CH218 (GN/VT), harness side.
- C271-1, circuit VH219 (GY), harness side and C271-3, circuit CH217 (BN), harness side.
- C271-2, circuit CH218 (GN/VT), harness side and C271-3, circuit CH217 (BN), harness side.
- Are the resistances greater than 10,000 ohms?
Yes
GO to S7.
No
REPAIR the affected circuits for shorts. TEST the system for normal operation.
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S7 CHECK THE HVAC MODULE HIGH BLOWER OUTPUT
- Connect: HVAC Module - DATC C228b.
- Connect: Blower Motor Speed Control C271.
- Ignition ON.
- Adjust the blower motor speed to HI.
- Measure the voltage between ground and HVAC module - DATC C228b-4, circuit CH217 (BN), harness side by back-probing the HVAC module - DATC C228b.
- 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 ground and HVAC module - DATC C228a-15, circuit CH218 (GN/VT), harness side by back-probing the HVAC module - DATC C228a.
- Is the voltage greater than 1 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 MODULE CONNECTION
- Carry out the HVAC Module - Dual Automatic Temperature Control (DATC) Cold Boot Process. Alternate Diagnostic Methods - HVAC Module - Dual Automatic Temperature Control
- Carry out the HVAC Module - Dual Automatic Temperature Control (DATC) On-Demand Self-Test. Alternate Diagnostic Methods - HVAC Module - Dual Automatic Temperature Control
- Operate the system.
- Does the concern return?
Yes
INSTALL a new HVAC module - DATC. 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.
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