Pinpoint Test M: The Auxiliary Blower Motor Is Inoperative
Climate Control System
Pinpoint Test M: The Auxiliary Blower Motor is Inoperative
Refer to Wiring Diagram Set 54, Manual Climate Control System for schematic and connector information. Diagrams By Number
Refer to Wiring Diagram Set 54, Manual Climate Control System for schematic and connector information. Diagrams By Number
Normal Operation
The auxiliary blower motor relay coil receives ignition voltage and a continuous ground. Battery voltage is supplied to the relay switch contact. When the relay coil is energized, voltage is delivered to the blower motor. Ground for the blower motor is provided from the blower motor resistor in LO and MED and directly from the blower motor switch in HI.
This pinpoint test is intended to diagnose the following:
- Fuse(s)
- Wiring, terminals or connectors
- Auxiliary blower motor relay
- Auxiliary blower motor resistor
- Auxiliary blower switch
- Auxiliary blower motor
PINPOINT TEST M: THE AUXILIARY BLOWER MOTOR IS INOPERATIVE
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M1 CHECK Auxiliary BLOWER MOTOR OPERATION
- Ignition ON.
- Check for auxiliary blower motor operation in all speeds.
- Does the auxiliary blower motor operate in any speeds?
Yes
GO to M9.
No
GO to M2.
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M2 CHECK FOR VOLTAGE AT THE AUXILIARY BLOWER MOTOR FUSE
- Ignition ON.
- Using a test light, check for power on both sides of Central Junction Box (CJB) fuse 159 (20A).
- Does the test light illuminate on both sides of the fuse?
Yes
GO to M6.
No
If the test light only illuminated on one side of the fuse, REFER to the Wiring Diagrams to identify the possible causes of the circuit short. If the test light did not illuminate on either side of the fuse, GO to M3.
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M3 CHECK THE VOLTAGE TO THE AUXILIARY BLOWER MOTOR RELAY
- Ignition OFF.
- Disconnect: Auxiliary Blower Motor Relay.
- Ignition ON.
- On early build vehicles, measure the voltage between ground and:
- Auxiliary blower motor relay pin 1, circuit 15-NC12 (GN/YE).
- Auxiliary blower motor relay pin 3, circuit 30-NC9 (RD).
- On late build vehicles, measure the voltage between ground and:
- Auxiliary blower motor relay pin 1, circuit 15-NC12 (GN/YE).
- Auxiliary blower motor relay pin 3.
- Are the voltages greater than 10 volts?
Yes
GO to M4.
No
On early build vehicles, VERIFY Battery Junction Box (BJB) fuses 1 (25A) and 10 (30A) are OK. If OK, REPAIR circuit 15-NC12 (GN/YE) or 30-NC9 (RD) for an open. TEST the system for normal operation. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short. On late build vehicles, VERIFY BJB fuse 7 (20A) is OK. If OK, REPAIR circuit 15-NC12 (GN/YE) for an open. TEST the system for normal operation. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short.
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M4 CHECK THE GROUND TO THE AUXILIARY BLOWER MOTOR RELAY
- Ignition OFF.
- On early build vehicles, measure the resistance between auxiliary blower motor relay pin 2, circuit 31-NC12 (BK) and ground.
- On late build vehicles, measure the resistance between auxiliary blower motor relay pin 2, circuit 31-NC12 (BK) and ground.
- Is the resistance less than 5 ohms?
Yes
GO to M5.
No
REPAIR circuit 31-NC12 (BK) for an open.
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M5 CHECK THE AUXILIARY BLOWER MOTOR OPERATION WITH THE RELAY BYPASSED
- Ignition OFF.
- On early build vehicles, connect a fused jumper between the auxiliary blower motor relay pin 3 and the auxiliary blower motor relay pin 5.
- On late build vehicles, connect a fused jumper between the auxiliary blower motor relay pin 3, and the auxiliary blower motor relay pin 5.
- Does the auxiliary blower motor operate correctly?
Yes
INSTALL a new auxiliary blower motor relay. TEST the system for normal operation.
No
On early build vehicles, REPAIR circuit 30S-NC9 (RD/GN) for an open. TEST the system for normal operation. On late build vehicles, VERIFY BJB fuse 2 (40A) is OK. If OK, REPAIR circuit 30S-NC9 (GN/RD) for an open. TEST the system for normal operation. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short.
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M6 CHECK THE GROUND TO THE AUXILIARY BLOWER MOTOR
- Ignition OFF.
- Disconnect: C327.
- Measure the resistance between C327-2, circuit 31S-FA73 (BK), harness side and ground.
- Is the resistance less than 5 ohms?
Yes
GO to M7.
No
REPAIR circuit 31-FA73 (BK) for an open. TEST the system for normal operation.
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M7 CHECK THE VOLTAGE TO THE AUXILIARY BLOWER MOTOR SWITCH
- Disconnect: Auxiliary Blower Motor Switch C3198.
- Ignition ON.
- Measure the voltage between auxiliary blower motor switch C3198-4, circuit 30-DA1 (RD), harness side and ground.
- Is the voltage greater than 10 volts?
Yes
GO to M8.
No
REPAIR circuit 30-DA1 (RD) for an open. TEST the system for normal operation.
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M8 CHECK THE OPERATION OF THE AUXILIARY BLOWER MOTOR WITH THE AUXILIARY BLOWER MOTOR SWITCH BYPASSED
- Ignition OFF.
- Connect a fused jumper between the auxiliary blower motor switch C3198-4 and the auxiliary blower motor switch C3198-2.
- Ignition ON.
- Does the auxiliary blower motor operate?
Yes
INSTALL a new auxiliary blower motor switch. REFER to Section 412-01. TEST the system for normal operation.
No
INSTALL a new auxiliary blower motor. REFER to Section 412-01. TEST the system for normal operation.
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M9 CHECK THE OPERATION OF THE AUXILIARY BLOWER MOTOR SWITCH IN LOW POSITION
- Ignition OFF.
- Select low speed on the auxiliary blower motor switch.
- Measure the resistance between auxiliary blower motor switch C3198 pin 4, component side and auxiliary blower motor switch C3198 pin 3, component side.
- Is the resistance less than .5 ohms?
Yes
GO to M10.
No
INSTALL a new blower motor switch. REFER to Section 412-01. TEST the system for normal operation.
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M10 CHECK THE OPERATION OF THE AUXILIARY BLOWER MOTOR SWITCH IN MEDIUM POSITION
- Select medium speed on the auxiliary blower motor switch.
- Measure the resistance between auxiliary blower motor switch C3198 pin 4, component side and auxiliary blower motor switch C3198 pin 1, component side.
- Is the resistance less than 0.5 ohms?
Yes
GO to M11.
No
INSTALL a new auxiliary blower motor switch. REFER to Section 412-01. TEST the system for normal operation.
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M11 CHECK THE OPERATION OF THE AUXILIARY BLOWER MOTOR SWITCH IN HIGH POSITION
- Select high speed on the auxiliary blower motor switch.
- Measure the resistance between auxiliary blower motor switch C3198 pin 4, component side and auxiliary blower motor switch C3198 pin 2, component side.
- Is the resistance less than .5 ohms?
Yes
INSTALL a new auxiliary blower motor. REFER to Section 412-01. TEST the system for normal operation.
No
INSTALL a new auxiliary blower motor switch. REFER to Section 412-01. TEST the system for normal operation.
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