As you enjoy your Recreational Vehicle, the years and the miles start to show themselves in the outside lights. Running lights flicker, then fail completely; backup lights work sporadically; indicator and stoplights do not always give fair warning to other motorists.
ALWAYS START BY CHECKING THE BULBS.
If a bulb is blown, it will never work but if it works on and off, and the filament inside is sound, suspect bad connections.
No need to rush over to a repair shop to get the connections repaired. This is a job you can do yourself, even with no electrical knowledge. Repair shops like to make it look like a very tough job when, in fact, it is one of the simplest tasks.
WARNING: if the shop starts talking about re-wiring your lights, jump in the cab and drive away as fast as you can. Either they do not know what they are talking about, and will wreck your vehicle, or they have marked you as an easy dupe and are about to take you for a lot of money. Here is why:
1. The wiring of the outside lights is very solidly done at the factory. The wires are stapled in place and will likely never need replacement. Almost all troubles with outboard RV lights are due to faulty ground connections, which are easy to remedy.
2. An outboard light has one wired connection, carrying the +12 volt battery supply. This is the only actual wire connecting to the bulb fixtures. (Two wires for brake-signal-backup bulbs.)
3. The connection to the negative side of the battery (the ground return) is through the vehicle chassis. In other words, the battery is grounded to the chassis, and the electrical circuits are normally grounded to the chassis, as well. This makes it simpler to supply power to the circuits; only one physical wire needs to be routed to each device. The negative connection for an outside light is a simple sheet metal screw fastened through the grounded aluminum siding of the vehicle.
4. Are any of the other running and signal lights working? If so, the fuses are probably OK.
Again: make sure the bulbs are still good, and that the metal spring contacts are tight against the bulb contacts. Running lights have only one filament in the bulb, while the signal-brake-backup bulbs have two, and therefore two wires and spring connections to the back of the bulb.
THE USUAL PROBLEM? The grounding screw! The ground return is through a screw fastened to the weakest part of the system -- the thin aluminum exterior siding of the RV. Bumpy roads, rain, dirt, all help weaken the connections. The older the vehicle, the more these screws work their way loose. Once the ground screw starts to loosen even a little bit, the electricity starts to arc; corrosion gathers in the joints between the screw and the bulb connector, and between screw and chassis.
THE FIX? Clean up the connections. Here is how:
1. Remove the plastic light covers. The larger ones will have little tabs on either side: push in the tab on one side and gently lift the cover off. The small running lights will pry off with gentle pressure from behind any one of the sides.
2. Inspect the grounding screw and the metal connection to the light underneath it. You will likely see some corrosion, and the screw may even be rattling around loose.
3. Remove the screw and polish up the connection with some fine emery cloth (not sand paper) You want as smooth and shiny clean a surface as possible for good electrical connectivity. Look behind, at the screw hole in the aluminum siding. Clean that up, too!
4. Replace the screw with a new one of the same size. If the screw hole in the siding has been enlarged through miles of vibrations, or over-tightening, then use a screw one size larger in diameter. This will cut a slightly larger hole, making a clean, new connection.
NEVER USE A LONGER SCREW! You never know what you might puncture behind the aluminum sheeting!
Finally, tighten the grounding screw firmly in place, but not so hard that you strip the hole.
5. Older light covers have flat putty strips on the inside for waterproofing. (Most people prefer instead to run a thin bead of silicone caulking around the outside edge of the colored lens covers to keep dirt and moisture out.) Clean away all the old putty first, though.
6. It pays to check all of the running or signaling lights once you are at it. Re-tightening ALL the screws ensures that all your lights will function well for a long time to come.
While you are at it, clean all those colored plastic lenses: brush the dirt out and then give them a wash-up with a little dish washing liquid. Your outboard lights will shine like new.
Now you are ready for many more years of road running with safe lights, and you will avoid fines for improper lighting.