F 550 4WD Super Duty V10-6.8L (2009)
GO to AD6.
No
REPAIR circuit GD122 (BK) for an open. TEST the system for normal operation.
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AD6 CHECK FOR VOLTAGE TO THE TRAILER BATTERY CHARGE RELAY COIL (INOPERATIVE CONDITION)
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Ignition ON.
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Measure the voltage between the trailer battery charge relay pin 85, circuit CBP33 (WH/BN), BJB face side and ground.
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Is the voltage greater than 10 volts?
Yes
REPAIR circuit CAT14 (OG) for an open. TEST the system for normal operation.
No
VERIFY the SJB fuse 33 (10A) is OK. If OK, GO to AD7. If not OK, REFER to the Wiring Diagrams to identify the possible causes of the circuit short.
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AD7 CHECK THE TRAILER BATTERY CHARGE RELAY COIL VOLTAGE SUPPLY CIRCUIT FOR AN OPEN
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Ignition OFF.
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Disconnect: SJB C2280b.
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Measure the resistance between the trailer battery charge relay pin 85, circuit CBP33 (WH/BN), BJB face side and the SJB C2280b-6, circuit
CBP33 (WH/BN), harness side.
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Is the resistance less than 5 ohms?
