If your trailer is equipped with brakes, check them when you inspect the bearings. Examine brake linings and replace damaged and worn parts. Remember that wet brakes will not hold well, but applying the brakes several times at slow speeds will help dry them for when they are really needed. Trailer brakes are particularly useful whenever heading down any hill or canyon. Also check your vehicles brakes, since they tend to take additional abuse when pulling a trailer.
Electrical systems are subject to corrosion, wearing insulation, and rusted terminals.
State and federal regulations require all trailers to be equipped with tail, stop, turn, and side marker lights. When connecting trailer lights to the towing vehicle, use a special wiring harness for ease and attach the white ground wire from the connector to the trailer frame, avoiding use of the hitch ball as an electrical connection. At least once a year, trace the wiring system from the tow vehicle to the trailer, inspecting for bare wires, cracked or chafed insulation, or corroded terminals. Replace worn parts. Place a small amount of waterproof grease on plug contacts and bulb bases to prevent rust and corrosion.