To check on some common problems and how to fix them, we checked in with Dustin Hoover, of Legendary Trailer Repairs, and David Kendall, of Grote Industries, manufacturer of boat trailer lights sold at West Marine.

Here are the troubleshooting tips they offered:

If there are no lights at all:

Check the vehicle/trailer plug connection. Power isn't getting from the tow vehicle to the trailer so that connector is where the problem exists. Most of the time, it can be fixed by making sure the connector contact points are clean. Nine out of ten times, the problem is going to be right there at the front of the trailer. Another possibility is a bad fuse in the truck.

– Dustin Hoover

Many a morning, Dustin Hoover of Legendary Trailer Repairs, outside Annapolis, Md., is working beneath a boat trailer.

If the trailer lights are dim:

That's a pretty good sign of a bad ground. If all the lamps are dim the problem is likely at the beginning of the harness. If some of them or only one is dim, I would begin checking the ground at each individual lamp.

– David Kendall

Some lights are dim while others are bright:

The dim lights have a grounding problem that is probably caused by corrosion of the bolts holding the light assembly onto the trailer frame. Make sure to check for corrosion on the plate holding the light(s) that is secured to the frame.

– Dustin Hoover

Trailer lights are blinking that shouldn't be blinking:

This indicates you have crossed circuits between your marker lamp circuit and the turn circuit. I would check for areas of wear in the harness, or something protruding through the harness. If one turn signal is being used and the opposite signal is also activated, there could be a short in the system or a weak ground that needs to be inspected.

– David Kendall

If one bulb is out:

Chances are very good the bulb needs to be replaced since everything else is working. If the bulb is good, then look at the white terminals behind the light to ensure there is a clean connection.

– Dustin Hoover

Unplug at the Ramp?

This is a continuing debate among trailer boaters AND Kendall and Hoover are split.

Kendall says, "No": While a hot bulb hitting cold water can present a substantial shock to the bulb filament, it is important to consider when you are most likely to be launching your boat. Generally it is in the daylight, so you wouldn't have had your marker lamps on and the short amount of time that you would be using your "stop" or "turn" functions, the bulbs shouldn't have too much time to get excessively hot and would cool considerably between application of those functions.

Hoover says, "Yes": I always unplug the lights at the ramp. I know every new trailer light assembly says "waterproof" but the fact that I don't have power going through the trailer wiring means I'm going to have less problems. Just remember to reconnect the lights after you've retrieved the trailer. Also, make sure the connector plug to the tow vehicle isn't submerged when launching or retrieving your boat.