The DIY Corner: LED Indicator light for your RV or Trailer

Are you an RV'er or Travel Trailer camper?

This simple modification can save you a ton of headaches

 
Have you ever left your Bathroom light or Outside "Porch" light on when dry camping and drained your battery overnight? Worse, left your vehicle connected to your trailer and drained the tow vehicle battery as well?  (will not apply to your tow vehicle if running with a battery isolator or ignition switch relay cut-off.)

Here is a fairly simply modification to help give you a visual reminder. Using a 12V LED, it will light up the interior of your trailer in the dark. You can't miss seeing it.  If you have access to run a ground wire to your light switch this project is real simple.  Sometimes there is a grounded metal rib right at the location, making for a real easy project.

The LEDs are available at Radio Shack and on line. (Radio Shack:12V/20mA 4mm Red LED Model:276-270(A) @ $2.49 each) They also come in other colors. Get the type that has a threaded shaft and a metal washer and locking nut. Since my trailer is DIY I actually used regular house type light switches even though these are 12V DC light circuits.  Figured they are easier to find if I am on a trip and encounter a switch failure.  Plus I ran conduit to standard outlet boxes so I could replace wiring if ever I needed.  I simply drilled a hole in the switch faceplate to mount the LED (I use the unbreakable nylon type switch plate since the plastic type tend to crack when drilled)

Drill the proper sized hole in the switch cover (locating it with room for it to protrude into the box or wall, and not interfere with the existing switch and existing wiring. Some of you might have to make a hole in the wall and perhaps mount the LED to the wall, or fabricate a piece out of plexi-glass or metal to create your own mount, which can be installed over hole.  I advise drilling a test hole in some scrap to fit the LED.  Remove the LED Nut and pass the wires thru the hole.  The LED should catch near the face of the lamp and not pass all the ay through the hole.  Once you know you have the proper drill bit size, drill your actual hole(s),

You will need a ground (Vehicle -12V) There normally is not a ground wire run to RV/trailer light switches, all the way back to the battery source.  The ground might be off the light and most likely a short jumper to the a metal frame.  The entire metal frame should be a good source to run a wire to or from, and produce the ground you need at the switch.  If your metal trailer frame is not grounded to the battery as it should be to meet electrical codes, you need to do that first. 

If you are a wood constructed frame or composite wafered wall you may have to run a ground wire to your light switch in order to complete this project.  Know you can successfully get your ground before you start punching holes in your walls, paneling, or interior skin.

Observe your RV wiring color code for positive and negative voltages.  Some use Hot +12V on Red wires, and ground -12V on black wire black.  But this may not always hold true.  Verify with a meter if in doubt.  Once you have that ground wire in place, wire one side of the LED to the ground wire. Wire the other side of the LED to the switched +12V side of the light switch (not the always hot side of the switch), connecting to the same point as the existing wire that goes on to your existing overhead light.   Some simple LED's are polarity sensitive.  If the LED doesn't work you may have to reverse the LED leads.

A similar method can also be used on 110V circuits....using a 110V rated LED of course.  Wiring the LED between the switched hot 110V (Wire on switch side going to the regular light) and the 110V neutral commonly found wire nut connected in the box behind the switch.  In 110V AC wiring the "Hot" wire is normally Black.  The Neutral is normally white.  When in doubt use a meter, not your skin, to test.

In either case (DC or AC) do not work on the wiring with the circuit/wires energized. Disconnect the power source and test to insure it is off before proceeding. Double check your new wiring before re-applying power.. Test with a meter if possible before reapplying power.  If you don't know what you are doing get professional help.