When we are hooked up to shore power the battery in the camper will charge. When hooked up to the truck it won't. I've looked in the truck manual and replaced, what I believe to be, the correct fuse and still nothing. Maybe looking at the wrong fuse? All this seems to have started with a drained camper battery (left the antenna power button on). I hooked the truck umbilical power cord up to the camper and tried to run the slides out and they went out part way, then noticeably slowed down, like it was getting power from the truck for a bit, then blew a fuse and went back to the camper battery before draining it completely. I can hook up jumper cables from the truck to the camper battery and it gets power, just not when I hook up the seven pin. Everything else on the seven pin works, all lights and brakes, just not the battery charge. When I put a multimeter on the seven pin of the truck, I can't get any of the prongs to read anything, with the truck started (but lights and brakes on the camper work thru the 7-pin). I know the meter is working because I put it on the truck battery and it reads... 12.something volts. Truck is 2008 F350 SD Lariat V10.
Any thoughts or ideas are appreciated

 

With your results. The meter probably didn't have a good ground but the lights did. Grind a bare spot to get a good ground , then meter should work. Double check manual for fuse location. I've seen bad fuses right out of the box

 

It would seem the issue is the fuse in the truck. As Dave suggested, make sure you are checking the right one. I am sure you know your charge lead is dead unless the key is turned on. There is really nothing else in that circuit other than a fuse and a relay. Start at the fuse using your meter, before you move to the seven pin.

Steve

 

The fuse is under the hood. The one I'm looking for is a plastic, kind of rectangular unit with two slits in the bottom to plug into the box? To check the fuse, set the meter to DC and stick the leads of the meter in the prong slits of the fuse? Not real sure about using the meter. Layman's terms of how or what to set the meter on... Thanks

 

The fuse under the hood you can recognize is where I start. Not sure if you have a self-ranging or auto ranging meter. You are going to set it to Volts DC. If you have to set the range, choose the one that would include about 10-15 volts.

With you meter set correctly, put the red meter probe on each side of the fuse while you have the black probe tightly against a good ground (a chassis part, screws heads usually work, etc.) Your meter should read battery voltage on both sides of the fuse or close to it. If you get nothing try on a another fuse. If you still get nothing, you likely are doing it wrong.

So you don't have to worry about the role of any relay, do your testing with the key in the run position, so relays should be closed.

The owner's manual normally gives a good graphic of the fuses and what they do. That is what I work from.

Someone on the forum with your same year truck might chime in here regarding fuse location.