Re: Trailer Brake Controller necessary?
Having just bought a boat and a trailer with brakes, and having just wired my car up with the 5 wire plug to replace the 4 wire it came with, I think I can help here.
First, does the front of your trailer look like this:
If it does, it's a surge brake. When you hit the brakes in your car, the trailer pushes into your hitch, the front compresses and a cylinder pushes fluid to the brakes and slows the trailer.
Now, the extra wire on the 5 wire...The 4 wires are exactly the same, so even if you put a 4 wire connector up to your car (say you borrowed a friend's trailer or something), it'd still plug in. That 5th wire (mine was blue) goes to your reverse lights. What I did was cut the 4 wire off of mine, butt connected and shrink wrapped the same 4 colors off the 5 wire, and then ran the blue 5th wire to the taillight assembly and away I go.
What the 5th wire does is engage a solenoid in the trailer coupler which doesn't allow it to compress, and when you back up, it doesn't apply the brakes. You don't actually NEED that 5th wire, if you need to pull your trailer home without it or something, as you can usually use the safety pin from your hitch to insert into a hole in front of the surge section which will keep it from compressing.
From what I understand, you can back up normally on flat ground without the brakes engaging, but if you try to back up a hill, the tongue compresses and the brakes apply.
Anyway, that seemed like a convoluted post, but I hope it helps.
