Trailer Electrics: Make The Connection

Keeping the electrics on your boat and trailer shipshape can save you time and trouble later. Let these tips spark your enthusiasm.

Photo of a boat being towed ona trailerPhoto: Scott Sommerlatte

Solder On

Two key words to good soldering are "clean" and "shiny." A proper solder joint will be shiny bright. If it doesn't look right, it probably isn't and will cause trouble in the future.

Connect Better

Photo of applying silicone grease to the wire harness connection

We want the drivers behind us on the road to see our trailer lights working properly, so I periodically clean the electrical wire harness connection between the truck and the trailer. After I've cleaned it, I apply silicone grease to ward off moisture and protect and facilitate better electrical contact, which translates into more reliable and longer-lasting trailer lights.

Lights, Laws, And More Electrical Tips

Laws governing trailers — including the lights they must carry — vary from state to state, are subject to federal regulations, and are always subject to change. Know your jurisdiction and rig. You'll find a state-by-state summary here:

The two most common ways to blow out a bulb are by immersing a hot bulb in cold water and by letting corrosion cause a short. Some trailer lights can be removed before launching. Don't let the connector plug to the car touch the water.

Use only tinned stranded wire, which is more flexible and chafe resistant. Secure exposed wire every 18 inches to prevent chafing. Inspect the entire system twice a year for bare or chafed wire, and give all contacts a protective dab of silicone grease. Don't forget the spare bulbs and fuses.

When trailer lights begin to fail, consider a total system replacement. Just cut wires at the rear end of the trailer and use old wires to pull new system wires through the trailer frame. Simply hook up a new light kit, and you have a brand new system.

Consider adding a heavy-duty flasher to your tow vehicle to help avoid the strain on turn signals (some turn signals will slow down to a crawl after a tow vehicle has been hooked up.)

Going To Ground

The most common cause of trailer-light problems is a loose or disconnected ground wire.

  • Be certain you have a good connection from the white ground wire to the trailer frame, usually located at or near the tongue.
  • Chafing is the second most common issue. Check each wire run to be certain a wire clamp securing it to the frame or bend in the wire hasn't resulted in exposing bare wire.
  • The trailer wiring harness often gets mangled in storage when it droops to the ground and gets stepped on or run over. Replacing the wire harness is often easier than troubleshooting the small wires that converge in this area, which is factory assembled on most trailers.

Keep It High

No lighting system can tolerate repeated immersion, even those rated "waterproof." Saltwater is especially aggravating. Having the trailer lights removable or mounted high enough so that they don't get immersed goes a long way in reducing premature lighting failures. If that can't be done, disconnect them from the tow vehicle prior to backing down the launch ramp. Remember, heated bulbs can crack when touched by cold water.

Connection Cure

To make trailer-light connections 100-percent waterproof, dab liquid electrical tape on either end of the heat-shrink tubing.

Cord Keeper

Tying two extension cords together like this (right) keeps them from popping apart while you're running the buffer.

Clean Connection

Don't wait until a dark rainy night to discover that you have no lights from a faulty connection. Keep the copper contacts in your trailer-light plugs clean: Go over the male and female socket connections with a wire brush, and spray the sockets with a good, quick-drying electrical connector cleaner. 

— Published: Fall 2013


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