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Hi everyone, I ordered my first boat 3 months ago and it is now less than 2 months until I get it. The project I'm working on now is getting my truck wired for the trailer. It's still too cold to work on it, which in my excitement leaves me way too much time to think about it. Here's my idea. My truck has a 4 wire harness. It also has 5 wires which are taped up but labeled for trailer light hookup. My trailer will have a 5 wire connection. I'd like to use a t-connector to tap into the 3 wires in the harness to connect to the lights of the trailer on one connector and make a separate 2 wire connection using the backup wire(blue) and the ground(white) on another. This way when I get to the marina, I can pull the trailer lights connector when prepping the boat, insuring the lights will be cool when I put the trailer in the water. Leaving the backup light connection will let me maneuver the trailer without worrying that the trailer brakes will lock up. Is my idea sound? Secondly, would I even have to run the trailer ground wire to my truck? Couldn't I just ground that wire somewhere near the trailer tongue since the two vehicles would be grounded through the hitch? Please feel free to poke holes in my ideas.
Grounding through the hitch doesn't really make it. You need to wire the trailer ground to the vehicle. I have a 4 wire to 4 wire plug which worked fine with just drum brakes. After disc brakes were added I just added another wire, from my back up lights on the vehicle, to the wire from the lockout solenoid, on the trailer. When I get to a ramp, I just unplug the 4 way, and leave the other wire connected, so that the disc brakes don't lock up, while in reverse. Many people don't bother unhooking their lights, but I always disconnect mine.
Ngleo:
Would not recommend doing anything until you receive the boat & trailer. You could talk with the dealer and likely he knows what should come with trailer in the way of wiring connector. HOwever, manufacturer may change things. You could purchase what connector you believe to be correct, and then take this with you, along with a test light, to make sure you get connections right. But, as to your idea of making two different connectors, unplugging one and then plugging in the other at the ramp- I don't know, but would be very skeptical. A prior trailer we owned had a little lock-out knob for backing up. This was just regular brakes, not disc, and was set up for surge brakes. My present trailer has electric brakes-dual axel trailer and brakes on both axels. trailer manufacturer recommended leaving the connection in place at the launch- this will ensure I have brakes when backing down the ramp. I've followed this recommendation and have used this boat for 3 seasons with no problems. However, the bulb in the tail light is a sealed unit. Finally, as to the ground, I've experienced many problems when trailer lights were not grounded to vehicle. The only time this worked was when my "Ball" was sanded and very clean. However, at the end of the same trip, and coming home on interstate, noticed at dusk that trailer lights not working. Had to pull over, disconnect trailer, and again sand my hitch ball. Good luck....
I can tell you hw I hooked up mine. I guess it was a good plan since I have never had a light, brake or hookup issue.
I have five wires like you. Parking, R Turn/stop, L Turn/stop, Ground, and lockout for disc brake solenoid.
I took the wires on the truck supplied for trailer hookup from the factory and put ring terminals on them. I wired them directly to a 7 pin receptacle and mounted it on the truck. If your truck has a 7 pin receptacle which most now have, your done.
Then I put ring terminals on the trailer wires and wired them into a 7 pin plug. Use a little liquid electrical tape on the terminals and wrap the wires in a split loom.
Having no splices in the wires seems to help ensure the connections don't fail. Also, the 7 pin receptacle on the truck has a door that closes when not in use to keep water (and corossion) out.
Now, in 10+ years of owning trailer boats, I have never unplugged the lights before dunking the rig. I have never had one blow out because of it going in hot or whatever.
By the way, I have the type of lights that trap air around the bulb to keep water out.
I've had the current boat for 2 years and have had to do nothing to the lights or connections. They have been trouble free.
Unless you have electric brakes on the boat trailer it means not. I have a F-250 with a 7-pin and 4-pin standard. The boat trailer came with a five pin. As I said before unless you have electrical brakes on the boat trailer the 5th pin serves no purpose. You can rewire it browns to brown, greens to green and yellows to yellow oh and white to white thus back to a standard 4-pin or buy an adapter from wal-mart that will go from 5-pin to 7-pin if you have it or 5-pin to a 4-pin setup.
At least that is how my 5-pin boat trailer situation worked out..
Thanks for your answers guys. One thing that seems unanimous is to not ground the white wire to the trailer but all the way to the truck.
Mike F- I'm not an expert on the way electricity flows but on a 4 way plug, one of the wires is the ground wire. When the plug is pulled, wouldn't the circuit though the last(backup) wire be interrupted, rendering it useless anyway. That's the reason i thought to leave the ground and backup wires on their own connector.
krdriver- my trailer will have disc brakes on both axles but not electric and a 5th wire . It also has a pin to prevent the brakes from activating when backing up. If I forget to remove it though, I'll have no trailer brakes on the trip home.
PierP-Not having the 5th wire will mean the disc brakes locking up when trying to back up on flat ground.
The main reason I'm doing all this is because I've always heard the most common complaint about trailers is having to constantly replace the lights. I would like to disconnect the lights if it means they'll last longer.
Like I said above I have never disconnected the lights and never once had a problem. That topic has also been discussed here and lots of people never disconnect. Yes, we do fish in cold water so sometimes I'm dropping the rig into 38 degree water.
Extra harnesses and connections seem like another point that can invite corrosion, but maybe not.
For the trailer, I'd pay the extra and get the 7 pin installed at the factory, then hard wire install the 7 pin on the truck. And you are good to go regardless of 4 or a 5 wire setup.
There's got to be a good reason why all the big trucks use 7 pin connectors.
I have always unhooked my trailer lights before I backed it into the water. Why? Because my grandfather always did and he said that 99 times out of a 100 it would work fine but he did so just in case and because they might last longer.
wiring tow vehicle for trailer 
