Batt. hooked up while towing

[A2SuperCrew]

Possibly.  If the trailer has an inadequate ground (using the ball/coupler is inadequate), then having the headlights (which would include the running lights) would put more current through the ground, causing it's voltage to rise.

The ground wire should always be AT LEAST one size larger than any other wire to the trailer, because it is carrying all of the return current of all of the other wires.  Having good connections is also very important.

Austin

BINGO!  I don't have a seperate ground wire..........  Sometimes it's the simple things.  Can I just buy a ready-made wire with a clamp to do this?  I did a quick Google, and didn't see anything off the shelf.

Thanks AustinBoston.

[wavery]

BINGO!  I don't have a seperate ground wire..........  Sometimes it's the simple things.  Can I just buy a ready-made wire with a clamp to do this?  I did a quick Google, and didn't see anything off the shelf.

Thanks AustinBoston.

You could. Chances are you may forget it though :banghead: . I know I would, at least half the time.

It's better to wire it in to your harness.

[chip]

BINGO! I don't have a seperate ground wire.......... Sometimes it's the simple things. Can I just buy a ready-made wire with a clamp to do this? I did a quick Google, and didn't see anything off the shelf.
 
Thanks AustinBoston.

Um.  Was the truck factory wired for the tow package?  OR did you have to install the hitch and connections?   If a factory tow package, with the seven pin connector already there, it should have been wired with a ground.  Same for the trailer-it's an '06, with a round, Bargman-type seven pin connector?  
 
Just another thought-make sure the charging relay is installed in the Ford.

[A2SuperCrew]

Um.  Was the truck factory wired for the tow package?  OR did you have to install the hitch and connections?   If a factory tow package, with the seven pin connector already there, it should have been wired with a ground.  Same for the trailer-it's an '06, with a round, Bargman-type seven pin connector?  
 
Just another thought-make sure the charging relay is installed in the Ford.

The truck is factory wired with the seven pin plug.  I'm in shock!  The charging relay is NOT installed!  It was in a plastic bag with the brake controller wiring harness.  Why the heck wouldn't Ford install the relay from the factory?  I had no idea I needed to install the relay.  The instructions are buried three pages into the brake controller instruction packet.  I assumed the whole bag was for adding a brake controller since that's what it says on the cover of the instructions.  I guess it's not truly "Tow & Go"!!!

Thank you so much for this information, Chip!  

This web site is just awesome.  It would take YEARS for new PUP owners to figure all this stuff out without this great resource!

[AustinBoston]

Why the heck wouldn't Ford install the relay from the factory?

Because it's cheaper to hand it to you in a bag.  :eyecrazy:

In any case, that is something I just learned recently, and I've been around here for years.  And it explains your entire problem.  And I didn't think of it.  

But...you will never forget it, will you?  So the next time someone is asking about why the fridge killed their battery, you can be the one to say "Did you install the charge relay that Ford gave you in the bag?"  That's what really makes this a great site...there's a collection of us that learned things the hard way (or learned from soneone who learned things the hard way), and tell about it.

Austin

[chip]

Glad I could help.

Wish I could claim some experience with that particular problem, but like AB says, we all learn a little something here.  (I didn't know where you would find the relay, but I knew you had to install it. )
 
I learned about the relay on this forum during one of the many, many discussions that take place about brake controllers.
 
Happy camping!