I just installed some Blue Water LED's on my boat trailer and had the wires on the trailer run to a new 5 way flat so they would come on when I shift to reverse. Well my F150 only has the round plug (big fat plug) and the 4 way flat plug. Do I need to buy an adapter for the big fat round plug or can I install a 5 way flat plug to replace the 4 way flat? Is this something like Uhaul can do?

i would try a 12 dollar attwood 7 to 5 plug adapter

Just get an adapter. I have and adapter on my round plug that has the 4 way and 5 way!

I may go hit Autozone or Oreilys

Go to Tractor Supply

I have one here in Denton, I forget about them... apparently it�s a special order item... Oreilys got it ordered today, should be here in a few hours. I didn�t know I was looking for a unicorn

Well I have tried three different 7 blade to 5 pin adapters, still no reverse lights... I may take the truck and boat to Uhaul and have them diagnose the issue, they changed from the 4 pin to the one I have now. It shouldn't be this difficult should it?

i know the lights work, Mcgill in Lewisville hooked them up while it was at their shop and they showed me... Maybe I am just getting frustrated

Check the reverse fuse ?? For the tow package .

on the truck, a 4 way plug is not going to have a back up lamp. the 7 way does . i don't think you have a 5 way wishbone split harness on the trailer if it was originally a 4 way plug. the 5 way plug has got to go if your new lamps have a reverse lamp and wire. the trailer will have to plug into the 7 way receptacle to get reverse lamps. what your gonna need is a 7 way plug on the trailer harness. what i need to know is what 5 colors of wires you have on the trailer harness now?