Installing a dimmer switch

[Lightning55]

Need some expert advice to install a dimmer in my Grand Design Reflection 31MB. The 12v cabin lights in the ceiling are way too bright. The switch is a blue lighted switch in the main panel in the hallway. I want to install the new on-off/dimmer switch. I can easily run wires in the wall to a more convenient location about 3 feet away. Behind the main switch is 2 red wires (constant power to the switch and one that goes to the lights when the switch is turned on - see pic. The 2 white wires plugged into the current switch are probably ground?
I thought I'd just eliminate the main switch in the control panel and use the new switch for on-off and dimming.
How the heck do I wire this up?

[Jakehollingswor]

The reflection uses the ONECONTROL system so the blue light switch (load) wire is actually a signal wire going to the unity box in your basement. Its a bit more involved then taking wires off switch and running them to a dimmer. Can be done

[2112]

On the back of your panel switch, the white wire is ground (for the blue switch light), the center red wire is 12V, and the bottom red wire goes to your light. Verify this with a volt meter. With the switch off (no blue light) you should measure 12V from white to center red wire but not from white and the bottom red wire. With the switch on you should measure 12V from white to both red wires.
That is how mine is wired.

[dieseltruckdriv]

If you aren't set on using the switch you have, I have used 4 of THESE in my 5er. It has a description for either a 2 wire or 3 wire hookup.

I also carry a spare in case I want to add a dimmer to an led light I hadn't thought of yet (or been told one needed to be able to be dimmed).

Edited to add: I used the two wire hookup on all my lights.

[RickLight]

Have you tested the voltage of each wire against a known ground?
Is there already some additional switch for the light?

[Lightning55]

No luck so far. We've tried every combination to wire up this dimmer and can't get it to work. Very frustrating. We think it's a ground circuit issue.
I hate to give up but don't know what else to do.

[wopachop]

The 2 white wires to the switch are not negative?
I dont see why its not able to work.
1 of the red wires to the switch will be your 12v postive.
The other red wire will be your PWM V+ going out to the light.

[C_Schomer]

The neg. to the lights can't be tapped into or seperate the neg. that goes only to the lights I want to dim... It's all in the ceiling and walls. I can only access the POS. At the switch. Is dimming possible? I could use lightning55s switch if it's for LEDs... I would only needed a neg. to the switch, according to the diagram. Thanks!

[C_Schomer]

Ooopps, double post

[ScottG]

12V LED dimmers will have both + & - inputs and outputs. If it only hooks up to one or the other, it's not LED specific and wont work right.
The switch can be wired as usual, through only one side.

[C_Schomer]

Lightning 55 please post ordering info for that switch...that's exactly what I need. I ordered a dimmer for my ceiling LEDs and it does the dimming through the gnd. wire instead of the 12+. The wiring and color codes are right on the back of your switch. I hope it's rated for LEDs.
My light switch panel has no gnd... Just 12 POS coming in and all the switch legs going out but it will be easy to pull a neg.
I found an awesome 5k temp/5300 lumens dimmable led sticky strip to convert my fluorescant ceiling lights. Super white, no hint of blue or yellow. Ill try to find the info from Amazon for anyone who's interested.
Here it is to copy/paste
https://www.amazon.com/gp/product/B00PUY74TG/ref=ppx_yo_dt_b_asin_title_o00_s01?ie=UTF8&th=1

[ScottG]

Bobbo wrote:
My sister called me in a panic because she replaced a lightbulb in a ceiling fixture (stick and brick, not RV) with an LED bulb and there was a HORRIBLE sizzling noise, then the light went out. I went over and noted that the light had a dimmer switch and the LED bulb was not dimmable. Replaced the dimmer switch with ON/OFF switch, threw away ruined LED bulb, and all was well.

If a dimmer for an incandescent bulb is used, it will indeed fry the LED. Using an LED dimmer like the OP has purchased will work fine. All 12V LED's are capable of being controlled by that style of dimmer as long as the load is within the dimmers range - 10A in the case of the OP's dimmer.

[Bobbo]

My sister called me in a panic because she replaced a lightbulb in a ceiling fixture (stick and brick, not RV) with an LED bulb and there was a HORRIBLE sizzling noise, then the light went out. I went over and noted that the light had a dimmer switch and the LED bulb was not dimmable. Replaced the dimmer switch with ON/OFF switch, threw away ruined LED bulb, and all was well.

[wnjj]

Unplug the white wire(s) from the existing switch. If the ceiling lights still work but the blue light in the switch does not, that is the ground wire.

If that’s the ground wire, connect it to the black wire on the new switch. After that, determine which of the red wires is 12V by checking with a voltmeter. That wire goes to red on the new switch and the other goes to white. If you don’t have a meter or test light, just hook one red wire to red and the other to white on the new switch. If it doesn’t work, swap them.

[ajriding]

be careful with colors. Looks like in your pic the "electrician" just used whatever color wire was close.
Typically RVs use white wire for all ground. So, yours is different already, you cannot go by color, test everything first.
Agree on dimmers not always working with LEDs. Some dimmers make noise when dimmed.
You could always just get a less bright light bulb.... I started to call it a "dimmer bulb" but that would not work here.