Power to trailer? - Diesel Forum

stevebo55 · 07-05-2007, 12:24 AM

Gents,
I just bought a cargo trailer with interior lights. I am using the 7 pin plug that came with my 04 F250SD. If the truck iginition is "on" I get interior lights in the cargo van. If the truck is "off" I get no lights. Does anyone know how I can configure my truck to deliver power to the 7 pin plug even if the ignition is off?

Thanks in advance.

steve

hiljoball · 07-05-2007, 02:40 AM

Does the trailer have a battery? If your trailer has electric brakes, it should already have a battery. Perhaps you have surge brakes.

It might be easier to add a battery to the trailer that is charged by the truck when under way. This is better as it prevents you running down the truck batteries and leaving you unable to start.

KVOM · 07-05-2007, 11:27 AM

You might check the truck side of the plug with a voltmeter to see if you have an unswitched 12v lead. If so you could bridge the switched and unswitched leads on the trailer side.

Steve F. · 07-05-2007, 12:12 PM

I wouldn't think Ford would leave 12 volt active at the plug with the key off. If that was the case and you had the trailer plugged in it would/could drain the batteries on the truck... As far as I know all Makes shut that (charging power for RV batteries) 12 volt down after the key is off and also I would have to assume the 12 volt power is activated by a relay, so even to power that relay "all the time" would kill the batteries as well over time if the truck was not running.