Wednesday, November 30, 2016

Mystery Switches in RV - Just What Do They Do?

    I was in my RV the other day to check that everything was OK. Storing it for the winter doesn't mean nothing can go wrong! I check for water leaks, critter intrusion and mechanical/electrical issues about once every two weeks. It's also a good idea to check your battery water levels and top up if needed with distilled water (especially if you are leaving them charging over the winter!). During my walk around inside I noticed the "odd" switch by the bathroom vanity sink. When I first bought my RV, I had NO idea what it did. Well, after almost a year..I figured it out....luckily!

See The Red Switch On The Left?
Turns out it was wired to turn on the outside light on the outside wall of the RV, opposite from the passenger side and the main door. It sits just above the access door for the water heater and close by the dump valves and connections. Good place for a light, but when I purchased the RV, it didn't work. Well, the switch on the light itself wouldn't turn it on....even replacing the bulb didn't help. You probably can guess where this is going. I had flipped the switch on the light a few times (it must have been in the off position initially) and then at some point flipped the switch by the vanity. The next evening I had stopped for gas and got out of the RV by the driver's side door. Lo and Behold, the light was on! Had likely been on since the day before! You really can't see its illumination from inside the RV because of my thermal covers so I had no idea it was on.

The Light Is Just Under And To The Left Of The Window
Well, I flipped the switch on the light itself and it turned off. At that point I was happy it was working (it's a good place for a light!). When I got back from the trip I looked into it a bit further. If I looked into the dark recesses of the vanity sink cabinet I could see the wires running from the "mystery" switch to the back of the outside light! Aha! One of the wires had come lose from its taped- up junction. Upon closer inspection I realized the switch was lighted and that disconnected wire controlled power to light up the switch! Aha, again! The idea was the switch outside was left on and the switch inside used to turn on the outside light when needed. The switch itself would light up to let you know it was on. Good idea.

But why put it in the vanity cabinet? I suppose it was the easiest place to do the wiring.....hey, at least I figured out what the switch actually did! I'll bet you all have some mystery switches too....Come to think of it...the one above the driver's seat was a mystery too....but that one I figured out!

Be Seeing You...Down The Road,

Rich "The Wanderman"


  1. I don't have any mystery switches in my MH. However, I have found numerous mystery wires and wiring looms to nowhere. Just this week I found a wire loom that simply ends with three wires and female plugs. One is 12v positive hot, one is 12v ground and one is 12 volt positive, no current. I can't find a switch that controls it, so mystery missing switch. This was actually a good find as I intend to use the hot and ground to provide power to my "new" electronic cabinet (old CD cabinet above Passenger seat). Moving the hotspot and router in there and off the dash to end dash clutter. By the way, Winnebago has complete wiring diagrams for their coaches online including wire codes. It turns out these mystery wires were for an optional powered sat dish, which my coach doesn't have.
    Your mystery switch post reminded me of a great "Married with Children" episode where Al and buddies destroy the Bundy house (as if that where actually possible) trying to find what a mystery switch does.
    Love your posts as they always seem to remind me of my own experiences. Maintaining an RV is an adventure.

  2. Monte,
    Thanks for your kind keep reading them, I'll keep writing them!

    That 12V positive one with no juice may very well be an ignition switched line. Try testing it with key off and key on. Is the 12 V positive feed from house or chassis battery(s)?

    Rich "The Wanderman"

  3. Hi Rich
    The 12v+ is on the house batteries which is what I want. Good suggestion on the ignition side for the other 12v+. I'll try it tomorrow. I didn't think I was going to use it, but it would be nice to know, 'cause one never knows what new project might need it.
    I am re purposing the old CD storage cabinet above the passenger seat to hold all our wifi/cell/internet stuff. No CDs anymore, too much bulk. All music digitized now.
    Keep the posts coming, I love hearing about other's projects and discoveries. Even/especially the ones that don't go well. Makes me feel better about my nimrod moves. ;-) I suppose the nimrod reference dated me. Oh well, I'm lucky to even remember Bugs Bunny.


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