Using a 5 pin trailer connection with a 4 pin vehicle connection

[Ronnie]

First, I assumed that my new “to me” tow vehicle, an expedition with factory towing system would have a round 7 pin connector, it didn’t. Instead it has a 4 pin connection. I discovered this yesterday when I went to hitch my boat trailer up to it for the first time. I must have 6 to 8 round to flat converters but surprised to discover that I never needed any of them.

I simply attached the 5 pin connection from the boat trailer to the 4 pin connection on the expedition and it worked fine. The 5th pin floats free but it is the reverse lead that disengages the surge brake solenoid, not a problem for me since my solenoid has been broken since I got the boat, I used a magnetic “D” key to keep the surge brake from engaging and the trailer doesn’t have reverse lights anyway.

I’m embarrassed to admit that it took me over 20 years and probably over $100 to figure out that I don’t need to use any 7 pin to 4 or 5 pin adapters at all in this situation.

 

[Evil Sports]

Yes the magnetic D key is a must have. I dont move my boat far to launch it so I put the D key in and dont even attach the connector.

 

[blacksapphirez]

mine came with a 7 pin on the trailer, so i had to buy a converter to change it to the 4 pin. leaving 3 wires hanging. I have tapped my reverse signal and made a quick connect to the reverse lock out.

I noticed I can't always put in my lock out key as the tongue was compressed just enough even when I pulled away. and if i have the key in all the time, no surge brake so...