Always check your travel trailer lights before you hit the road. If they don’t work, one possible cause is dirt or oxidation on the umbilical cord plug and/or receptacle contact points.
Make it a habit to clean the contacts with a wire brush or sandpaper. A Dremel tool with right bit will make the job easier (be sure the lights are off when you do this, otherwise it could blow a fuse).
Scrape off dirt and corrosion in the contact holes with an ice pick, rat-tail file or small piece of sandpaper rolled around a toothpick Then, dab a little grease on the prongs, push the connector together.
A little petroleum jelly or light waterproof grease spread on the surfaces will act as a barrier against air and moisture, retard oxidation and keep the lights operating longer.
Soldering all wire splices will help prevent problems with loose connections. Wrapping the splices tightly with electrical tape or heat-shrink tubing will seal out dirt and eliminate shorts.
To keep dirt from getting into the plug between uses slip a small plastic bag over the plug and secure it with a rubber band or tape.
You may want to read the following articles at RVbasics.com:
