No Power on 7-Way 12V Pin After Batteries Replaced

Question:

The interior lights on my trailer quit working after I changed the batteries in my 2012 f350 diesel truck. The A pin in the 7 pin does not have voltage. any thoughts? Is there an activate sequence for that circuit?

asked by: Eddy A

Expert Reply:

There isn't an activate sequence like what's seen in the later model Ford trucks with the 'smart' trailer connectors.

What Ford refers to as the 'Trailer Tow Battery Charge' circuit is protected by a 25A fuse in location # 90 in the power distribution box in the engine compartment. Most likely a short occurred in that circuit that caused the fuse to pop.

Check the trailer connector at the rear of the vehicle, make sure it isn't damaged or corroded. If you can see white or green corrosion on the pins, it's possible that the corrosion has spread to the interior of the connector and allowed two of the internal terminals to bridge, causing a short. Clean/repair/replace as needed.

Next, trace the 12-volt circuit on the trailer. Look for pinched wires or loose connections or cracked/worn wire insulation-anything that would allow the wire to short out to the trailer frame. Once the short is located and repaired, you should be good to go but you will want to find and fix it, otherwise you'll continue to blow fuses.

expert reply by: Mike L