I have a box trailer with 12 volt interior lights and a battery for the break away system that is charged off the same circuit. Everything works on the trailer except these items which did work on my Chevy. Does the Ford 7 pin plug have a constant hot wire as it should? If so, why is mine not hot and what do I need to do to fix this? Its a real pain having no lights in the trailer. BTW I have a new body style 04 FX4 super cab with the heavy duty tow package and yes I did put in the relay so my trailer brakes work. Thanks

 

Unlike Dodge and Chevy, Ford uses a key switched hot which will only charge your trailer when the truck key is on. This is so you won't drain your truck battery. If you are wiring a truck from scratch, most customers prefer this method. If you are wanting to use your interior lights when the truck is off you can easily install an aux battery in the trailer to power the lights when the truck is off. You can also wire this so when the truck is running it will re-charged.

 

fords 12v is NOT constant on the 7pin plug....it is so u dont run down your battery in ur truck overnight or something. it is only hot when the truck is on.....there is a relay in the pass footboard fuse panel....

 

I guess I never tried my interior lights with the ignition switch on. On my Chevy they worked all the time which was nice for when you just wanted to jump in for a second to grab something. Makes sense about not running the battery down when trucks not running but still a bit of a pain if I have to unlock the truck, turn on the key, then walk back to the trailer. I guess I'll have to look into installing a bigger battery on the trailer for this purpose that charges when I'm hauling it down the road. Thanks for the info.