Why Would Truck Battery Drain When Connected to Horse Trailer

Published 11/06/2019

Question:

I need help understanding why my brand new Dodge Ram 3500 diesel has a dead battery when I leave either of my horse trailers hooked up overnight. My Ford F350 diesel truck has never had that problem with the same 2 trailers the past 9 years Ive been towing with it. I feel so insecure horse camping with my new truck for fear of being stranded in the mountains with no cell service to get help. I dont feel that after spending that much money on a truck, that I have to pull the trailer plug every time I haul with it! Please give me your ideas.

asked by: Debbie T

Expert Reply:

Sounds like your Ford truck's 12 volt trailer wiring circuit shut off when the vehicle was turned off and your new Ram 3500 has this circuit active all the time.

Either way there's a circuit on your horse trailer that draws amperage when the trailer wiring is connected. Most likely lights or a battery which the lights can be turned off and the draw would stop.

You could use the isolation solenoid part # PK5231201 to turn the circuit off when the truck is off. It would install inline with the 12 volt circuit and then the center pin would run to a keyed power source which basically stops the circuit from being active until the vehicle is turned on.

expert reply by: Jameson C