Have a battery in the bumper pull for the interior and exterior lights, have cab over camper with battery. Batteries charge when we go down the road from the truck. Never have had an issue with camper discharging truck batteries. But, we had the truck batteries discharge twice now. Once, camper was plugged in to electric for the long weekend, the other time we were on battery power only.
Thinking I have some sort of relay out, that is allowing the truck batteries to draw down from use in trailer and camper. That sound right?
If so, where do I find these relays? Is this something in my fuse box?
2001 F350, dual battery, dual alternators
Just think that something with the new trailer is different than the old trailer, and causing this issue. If we don't fix it by next ride, I'll just unplug camper and un plug trailer from the truck for weekend
Posted 2010-12-19 10:54 PM (#128200 - in reply to #128196) Subject: RE: charging relay question
Expert
Posts: 5870 Location: western PA
Most Fords have a "Tow" relay that provides power to the trailer for charging when the motor is running, and opens when the motor shuts off. This prevents the truck's battery from discharging and the resulting no start you have experienced.
There are a couple of fuse boxes under the hood. If you look above where your feet would be for the driver, you'll see a large fuse box with 30 -40 fuses inside. Beside this box, in front of the master cylinder and usually inboard of the large box, you'll find two smaller boxes. One of these will have a small relay inside. It may be sticking closed when the motor is off.
The relay has the same terminals as do the fuses, and just pulls out. With a multi meter across its terminals, you can determine if the contacts are opened or closed. The relay is easy to replace.
charging relay question
