I have a New Crestliner thats only been in the water twice now. Last night we noticed the left brake light does not come on. The left turn signal and regular lights work, but go out when I hit the brakes? I just checked the bulbs and they are both good (2 bulbs. I don't know a lot about wiring ,but I'd think I wouldn't be having problems with this already!

Please help!

Sounds like a ground. There are some good posts that have been posted on the various automotive/boat n motors/ expert info forums, but I don't know how to create a link to other posts. Even though the unit is new, mistakes are made at the factory. Just be sure that you have good clean connections at your pigtail from truck to trailer, and make sure you have a good ground at both the truck and trailer. White wire is ground, brown is running lights, and I'm pretty sure yellow is left; green right signals. If your truck pigtail is cruddy, replace it using either solder and heat shrink tubing or heat shrink crimp connectors. If you don't have a test light, get one. They are inexpensive and are sold at any automotive parts store. A good test light will save a lot of time in getting to the bottom of simple electrical problems.

i would agree on the ground.

Signal and stop light are same light bulb, and wires. Do you have stop on the right side ?
When you put the signal to the left power goes to the Yellow wire on your plug and trailer, when you signal right it goes to the Green. When you press brake power goes to both Yellow and Green wires.
The brown is for tail lights, if they all light up it shouldn't be a ground problem.

One more thing- try hooking up the trailer to another persons truck to see if the lights all work correctly. If the problem remains the same, I would take the rig back to the dealer and request warranty work. If the problem goes away, the issue is with your truck and need to find problem there.

I had a similar situation happen over the weekend with my trailer lights. It ended up being a ground that was pinched in the trailer. I suggest trying what john.wells suggested on another vehicle. If you have a voltage meter I recommend poking around with that and try to find if the source of the problem is in the trailer or on your vehicle. I've had to deal with trailer problems almost monthly in the past with bulbs burning out all the time. I picked up the optronics led light set and it works wonders compared to my previous bulb setup. Happy troubleshooting!

Leech if ya want and ya get out to Diamond stop by,I'm retired got all the tools and can help answer some of your questions.Will get ya up & going also.I'm on dogfishbay south of resort.email in profile.

I had a simular issue last week. Ended up I had a bad fuse in the ford. They put in a seperate fuse for the left and rigt side trailer lights. No brake and no turn signal on the right side and switched out the fuse and we are running.

I think we found the problem tonight. Inside the trailer hitch where the ball sits there was some factory black paint that was up inside making for a bad ground. I took a screw driver and scraped some of the paint out, put back on the ball, and it worked! I hope this is all that it was.

Thanks for the feedback! Grounding accounts for a lot of electrical problems, and almost always the case for weird lighting behavior. Was the ground a direct contact from the ball to hitch? Or is there a wire from the harness to the trailer frame? If there is no wire from harness to trailer frame, I would add one.