In case you really want to geek out and see where the diagnosis is going I have a more thorough thread running on the Ford Truck forum where I found a lot of useful information on wiring, etc. I will probably do a bypass of the circuit.

Turn signal, trailer wiring problem - Ford Truck Enthusiasts Forums

I was thinking that Ford may have addressed the problem of the trailer draining the TV battery and put a relay in to solve the problem, after reading your info, it looks like that is what they did. My explorer doesn't have the factory tow package. I installed a relay in the trailer to prevent blowing the fuse when I raise the trailer top. If you wire yours direct put a 30 amp fuse in the line, and use #10 wire, also you will have to unplug the trailer before raising the top or you will blow the fuse, it may not at first because you have a new battery in the trailer but after some use it defiantly will blow the fuse. Trying to raise the top with a dead trailer battery may have caused the problem but if everything was working right the trailer battery should not have went dead, unless it's time was up and a cell opened in the battery.

If the relay turns out to be toast. Replace it and try this, if the relay isn't activated by the key, it may be activated by the factory brake controller if it has an on and off switch.

__________________
Rich
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(215TL) - 1995 21' TowLite
(2209T) - 2009 22' TowLite
99 Ford Explorer 4DR 4X4

Thanks PopRichie77, I'm going to run one last test today and then call it and run the wire as you suggest. What I find funny is that the +12V wire heading into the trailer adapter is tiny. #14 or #16 maybe? The ground looks like it might be #12 or #10.

Problem with my new plan is that I'll end up splicing that tiny wire (the 7 pin receiver is a one-piece rubbery mold - I'm not sure that it opens) so anything heavy gauge going in is almost pointless.

You can buy replacement sockets that come apart for wiring. I'd do that if your +12V supply wire is too small.

- Jack

Got it! I did a full writeup over on the Ford-Truck forum since it was more related to the wiring of the Ford. Thanks all for your help!

Good job, I would say that as long as you turn the key off first, you won't have to unplug the trailer to raise the top, as the relay disconnects it. Also when using battery power in the trailer it won't drain the TV battery.

With the trailer plugged in and the Expedition running, put the fridge on DC and check the voltage at the trailer battery should be a least 13 volts and at the fridge, should be over 12 volts. This will tell if the wiring is heavy enough.

__________________
Rich
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(215TL) - 1995 21' TowLite
(2209T) - 2009 22' TowLite
99 Ford Explorer 4DR 4X4