Pinpoint Test Ac: The Trailer Battery Charging Is Inoperative

WARNING: This page is about a different car, the 2006 Ford F550 Super Duty, 2006 Ford F450 Super Duty, and 2006 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.

AC1 CHECK VOLTAGE FOR THE BATTERY CHARGE AT THE TRAILER TOW CONNECTOR
- Key in OFF position.
- Disconnect: Trailer Tow C4099 (7-Pin).
- Key in ON position.
- Measure the voltage between the trailer tow C4099-5, circuit 49 (OG) and ground.
  
  Fig 1: Checking Voltage For Battery Charge At Trailer Tow Connector
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
Yes : The vehicle is operating correctly. SEND the trailer to an authorized camper/trailer repair facility.

No : GO to AC2.
AC2 CHECK THE TRAILER TOW BATTERY CHARGE RELAY
- Key in OFF position.
- Disconnect: Trailer Tow Battery Charge Relay C2110.
- Carry out the trailer tow battery charge relay component test.
- Is the trailer tow battery charge relay OK?
Yes : GO to AC3.

No : INSTALL a new trailer tow battery charge relay. TEST the system for normal operation.
AC3 CHECK FOR VOLTAGE TO THE TRAILER TOW BATTERY CHARGE RELAY
- Key in OFF position.
- Disconnect: Trailer Tow Battery Charge Relay C2110.
- Key in ON position.
- Measure the voltage between the trailer tow battery charge relay C2110-86, circuit 295 (LB/PK), harness side and ground.
  
  Fig 2: Checking Voltage To Trailer Tow Battery Charge Relay
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
Yes : GO to AC5.

No : VERIFY the CJB fuse 27 (15A) is OK. If OK, GO to AC4.
AC4 CHECK CIRCUIT 295 (LB/BK) FOR AN OPEN
- Key in OFF position.
- Disconnect: CJB C270a.
- Measure the resistance between the CJB C270a-12, circuit 295 (LB/PK), harness side and the CJB C270a-21, circuit 295 (LB/PK), harness side.
  
  Fig 3: Checking Circuit 295 (LB/BK) For Open
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
Yes : INSTALL a new CJB. TEST the system for normal operation.

No : REPAIR the circuit. TEST the system for normal operation.
AC5 CHECK THE GROUND TO THE TRAILER TOW BATTERY CHARGE RELAY
- Key in OFF position.
- Measure the resistance between the trailer tow battery charge relay C2110-85, circuit 57 (BK), harness side and ground.
  
  Fig 4: Checking Ground To Trailer Tow Battery Charge Relay
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
Yes : GO to AC7.

No : GO to AC6.
AC6 CHECK CIRCUIT 57 (BK) FOR AN OPEN
- Disconnect: CJB C270a.
- Measure the resistance between the CJB C270a-11, circuit 57 (BK), harness side and ground.
  
  Fig 5: Checking Circuit 57 (BK) For Open
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
Yes : INSTALL a new CJB. TEST the system for normal operation.

No : REPAIR the circuit. TEST the system for normal operation.
AC7 CHECK THE CJB
- Measure the voltage between the trailer tow battery charge relay C2110-30, harness side and ground.
  
  Fig 6: Checking CJB
  Courtesy of FORD MOTOR CO.
- Is the voltage greater than 10 volts?
Yes : GO to AC8.

No : VERIFY the CJB fuse 107 (20A) is OK. If OK, INSTALL a new CJB. TEST the system for normal operation.
AC8 CHECK CIRCUIT 49 (OG) FOR AN OPEN
- Disconnect: CJB C270g.
- Measure the resistance between the trailer tow C4099-5, circuit 49 (OG), harness side and the CJB C270g-6, circuit 49 (OG), harness side.
  
  Fig 7: Checking Circuit 49 (OG) For Open
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
Yes : INSTALL a new CJB. TEST the system for normal operation.

No : REPAIR the circuit. TEST the system for normal operation.