trailer light problem

[Rbsgfd578]

I have a strange trailer light problem and have been beating my head against the wall trying to figure it out.
The other night when leaving the lake my lights on my trailer were working fine,I got home and had not lights whatsoever on my trailer.I checked my fuse under the hood and it was blown, replaced the fuse and hooked my trailer lights back up and it blew the fuse.So know I was sure the problem was isolated to my trailer.I have a 7 pin to 4 adapter on my 1997 F-150.Replaced the fuse again without hooking the trailer up and my adapter plug has the 3 LEDs on it to let you know that its working fine here is the wierd part only the center LED lights up anymore, I want to think when I got this new adapter a few months ago all 3 LEDs would light up, so now im trying to figure out is the problem my trailer or my truck..If its my truck how do I go about troubleshooting it?
Thanks in advance for any help.

 

[Silvertip]

Re: trailer light problem

It is probably the adapter. There have been lots of issues with these. 7 pin truck receptacles are wired for RV use so they have a 12V circuit to charge trailer batteries, electric brake circuit, and some include a back-up light circuit to engergize a reversing solenoid when using a trailer with surge brakes. Replace the fuse, insert the adapter but don't plug in the trailer. Now use a test light to check each of the functions on the four pin outlet on the adapter. I'll bet you have at least one circuit that is not a turn signal or running light, or ground connection. Of course you should check the trailer first to make sure it's working properly. You can use a battery charger or a battery to do that.