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Mod #95: Water Heater On Lights

Posted By ModMyRV On February 20, 2010 @ 10:59 am In electrical, lighting | 14 Comments

This modification was designed and completed by ModMyRV member RVfor5. This article carries a copyright. Permission must be obtained from the author before duplication or reposting.

My RV has an Atwood Gas/Electric water heater in it. The switch has a light on it, but it only comes on when there is a problem in the system you have turned on. Because I have small children, and the switch is in the counter at their eye-level, I was concerned that they would turn the switch on or off without us knowing, either wasting resources when we don’t need the heater on, or making for cold showers when I’m expecting a warm one.

Mod Difficulty:

I figured that the solution was simply to put an ultra-low draw LED into the switch that lit when it was on. I wanted the light in the switch because it can be seen from everywhere in the cabin, keeping me from having to inch around to the wall that my manufacturer used for the control panels. I found the LEDs at Radio Shack (link below). There were a few that I could use, but these seemed to fit exactly what I wanted to do. They were small enough to be drilled into the plastic area around the switch. I decided instead of just putting one in (which anyone could do on any single-type water heater), that I’d put one each for each type of energy source.

Recommended Tools:

  • Digital Multi Meter
  • Screw/nut driver (depending on what your manufacturer uses to mount the switch)
  • Wire cutter/crimper
  • Misc 12v Wire connections (depending on preference)
  • ~1 ft. 18 ga. Automotive Wire (if you choose to lengthen the LED leads)
  • Drill with bit sized according to LED package
  • Needlenose pliers (make one step easier)
  • LED light(s)

First step was to gather all the materials. The two LEDS, connectors of whatever format you want to connect them (splits; blade connectors into tap-outs; straight tap-outs, or tying them together in another form depending on your preference – I used one butt-connector). One thing to be sure to have is a good crimper and good knowledge of 12v electric safety since an open connection could cause a fire. If you aren’t certain about what you’re doing in this mod, have someone who knows what they are doing do it.

Second, remove the switch plate from the cabinet, exposing the back of the plate and the wiring. Every RV manufacturer probably wires them differently with different color wires and different styles to bring power to the unit, so again, if you aren’t sure, get someone who is. I’m comfortable enough with 12v that I continued. Using a meter, I verified which connections were positive, and which were ground. Then I was able to discern the two different switched loads. My plan was to wire the positive side of the LED to the LOAD side of each switch, then tie the negative sides together with the other negative wires already tied together by the factory behind the plate.

IMPORTANT: Turn off battery power cutoff/disconnect the coach battery for the 12v switch, or, if necessary, unplug the RV or remove the fuse for the 120v side. Atwood switches are operated off a relay and turn off with the 12v cutoff/disconnect. Verify that there are no hot wires by checking all the connections with the meter.

The LED package tells you what the outer diameter of the post needs to be drilled to. There are several locations that you could choose to put in the LEDs, but I wanted to put them in the plastic between the light and the switch to keep it neat. I chose to leave everything intact while I drilled so that I could place the LED exactly where I wanted them. The front of the LED has a little lip so that it doesn’t slip through the mounting hole, meaning you have to plan on drilling the hole a little away from any non-flat part of the switch so that the LED will sit flat. I drilled my holes as even as I could and then used the nuts provided to tighten down the posts (needlenose pliers help with this, but fingers work).

I decided to remove the manufacturer connectors (Orange and White wires) and twist in the LED red wires to the respective load wires, then crimp new connectors on those, making sure that neither wire was loose by pulling lightly on it. You can see the connectors in the pictures. Tying in the black wires was a little more difficult because of two things. One, there is not a lot of space there; two, the leads coming from the LEDs are fairly short. From the photo you can see how the ground wires are tied in – I cut the factory connector off the wire going to the switch, then tied the two led wires together, butt connecting them to the factory wire. Though there are a number of ways to do this, I chose the method I did because I thought it offered a better connection. Tying the two 18ga. LED wires together allowed me to just use the standard size butt connector with the factory 14ga. wire. Before putting the switch back in place I turned the 12v back on and tested the water heater with each switch, running the heater long enough on both switches to be sure there wasn’t a failure to the middle red light. I replaced the switch making sure that the wiring was tied up above the drawer below so that nothing got caught.

The two LED lights work great and aren’t so bright as to be distracting at night. I know when the kids turn on the water heater, and it turns out to be a reminder not to waste resources when I don’t need to use them. All in all a win-win for only about an hour of invested time, and about $6 in materials.

ModMyRV recommends these parts for this mod:

Crimp Tool and Connectors Package
Green LED with Holder - Flat
Green LED with Holder - Rounded


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