Sounds like it is like most EZ-loader trailer. Surge brakes. The
coupler where you attached to the tow ball slides and activates a master
cylinder to provide braking. The 4 wire plug has a ground wire in the
rubber shielded connector and the other 3 are running lights and brake /
turn signals for left and right.

"Tom" wrote in message
...

I "think" mine has 4-wires. The plug of the wiring has 3 exposed metal
prongs sticking out and 1 black plastic prong that may or may not have
any metal thing inside. What does this tell me anyway?
It sounds like you have no brakes at all. Generally, electric brakes
have additional wiring running to a control unit and surge brakes have
additional wiring tied to the backup lights that release the brakes in
reverse (pushing the trailer backwards has the same effect as the
trailer pushing the vehicle when stopping.). I won't guarantee this is
always the case but has been the setup on rigs I've seen. Take a look
at the back side of the wheels and see if there is anything that
appears to be a brake with a line of some type running from the wheel
to the tongue of the trailer. Disc brakes are easy to see - a disc
with a caliper mounted - drum brakes would be enclosed. If all you see
is the axle with a spindle attached and the wheel bolted on then you
have no brakes and nothing to worry about.