How often have you seen someone towing a trailer when the lights didn’t work? I’ve seen it a lot. It’s downright dangerous, and with a little maintenance, and checking them before each trip, you can keep your lights working A-OK and be safe!
Again, the first thing to do is to check the lights every time you connect your trailer. Make sure the connection is tight, and the plug is locked in (if it has a locking tab). Keep the plug on your trailer clean and corrosion free by keeping it wrapped up in a bag when not in use. Make sure the door on your tow vehicles trailer plug closes well. Keep it as clean as you can. Applying a dielectric grease will help preserve the connections. If there is corrosion, use an electrical contact cleaner and a very small wire brush to clean the contacts, after you have disconnected the vehicle’s battery!
While you’re at it, have a look at the trailer wiring harness. Look for abrasion damage, and to make sure the plug isn’t separating from the cable. If you see any damage, have the cable checked and replaced if needed.
When connecting the wiring harness to your tow vehicle, make sure it stays sufficiently off the ground. If it hangs too low it can get caught on road debris or chafe on the road surface. Similarly, if it’s too tight it can pull the cable free from the tow vehicle on a sharp turn with the trailer, so make sure the cable has enough slack to be able to move with the trailer, but not so much that it can get caught on the road!
Lastly, the lights on your trailer can leak and get dirt inside, causing them to become dim. Try to keep them sealed up with a little silicone sealant where the lens meets the base. If they get dirty and dim, take them apart and clean them and replace the bulb, or the fixture if its broken or brittle. LED’s are a great option here for replacements, and most fixtures are easily replaced by new ones.