trailer lighting issue

So it’s been about 4 weeks since the boat has moved from the garage. Today I hooked up and noticed the only lights working on the trailer is the 2 amber side marker lights. No tail lights, brake lights or turn signals. The fuses in the truck look ok. Anyone have any input on this? Thanks!

Bad ground, most likely rust in the coupler. Best thing to prevent this is hook up a dedicated ground wire.

Grab a piece of wire that’s long enough to reach from the light assembly on the back of the trailer all the way up to the truck. Connect one end to one of the mounting screws for the light (it’s usually a 1/4 inch bolt, 7/16th nut) and the other end to ground on the truck connector. If the lights work, then there’s a bad mechanical connection in the trailer somewhere between the amber lights and the rear. Like HuntinDave said, a dedicated ground wire is a good idea and will solve a lot of present and future problems.

SR

Give the trailer light plugs a shot of wd-40 and plug/unplug them several times to remove any corrosion on the terminals – and I agree with running a dedicated ground wire instead of relying on the trailer ball/hitch connection.

Don’t forget to check the bulbs.

The fact that the amber lights are working means you are getting tail light power past both the truck plug and the trailer plug. I would say that the problem is at the light. Look under the trailer to see if a ground wire on the light is riveted to the trailer frame. It is common for calcium to get between the ground wire and the frame. I’ve drilled out rivets, buffed the frame and put back together with dialectric grease and bolt/nut.

Thanks guys. I think there is a ground wire to the frame on both tail lights. I’ll try cleaning those up and look at running a dedicated ground wire. We’ll see what happens tonight!