3 way dimmer - 12 volt

mrsjpmrsjp Registered Users Posts: 1
Hi there,
I’m hoping someone on here can help me...

A little bit of background - I have a backcountry is ski lodge in Canada, fully off grid. I am intimately familiar with my solar setup and all of the house wiring. I’m not inexperienced, but I’m also not an electrician! I have successfully wired lots of three way switches...

Anyway, my problem is this:

I am installing a 12 volt three way dimmer switch-   this one to be specific: (https://www.superbrightleds.com/moreinfo/single-color-dimmer-switches/slvdx-60w-3w-led-3-way-switch-and-dimmer-for-standard-wall-switch-box/1245/2916/

I can get it to work as a 3 way but it won’t dim the lights. The bulbs are 12 volt dimmable bulbs and I have tested them, they dim with this particular switch when I hook it up as a single pole. 

The dimmer switch is installed in the j box where the home run comes in. Power goes from here to the j box with the other switch via a 3 wire. Then the power is carried to the light with a 2 wire.

Both j boxes are multi gang with switches going to other strings. I am wondering if the problem is that with all the other power coming into, and going out of these boxes... that unless my string with the dimmer on it is completely isolated, the signal to change the voltage is basically over ridden and full power continues to be delivered to the lights? I’ve never heard of having to isolate a string for a dimmer on AC even when the switch shares a box with other strings...

As I said, I can get the switch to work in a 3 way
configuration, and I can get it to dim the lights, I just can’t get it to do both at the same time!!


  • BB.BB. Super Moderators, Administrators Posts: 33,268 admin
    I assume wired per this drawing (from your link):


    And your LEDs are 12 or 24 VDC, with a maximum load on the dimmer of 2.5 amps (if I read the specifications correctly)--Or I would get 60 Watts max on 24 volt or 30 Watts max on 12 volt circuits.

    If the DC output of the dimmer has been shorted, it might either kill the DC output (open) or kill the dimming function (just 3 way switch function working).

    I assume you have the input and output leads wired correctly to input (DC power) and output (lamp, or 3 way switch+lamp load).

    In general, DC power lines are to be "isolated" from AC power lines (and J-boxes). You don't want an 120 VAC short to your 12/24 VDC system (it is generally unsafe). The AC lines to your AC to DC converter is in AC side, and the DC output goes to a separate J-Box with your DC dimmer/switches.

    I have seen issues were very small leakage current can case LEDs (and twisty florescent lamps) to blink or light (at very low light levels).

    When you have the "failures"... And further observations (aka dimming works, but three way switch simply is On/On no matter how switch is thrown).

    One other possible issue... There are very common 120 VAC to 12 VAC transformers (used for track lighting). And there are 120 VAC to 12 VDC converters (for your DC only lighting). You are sure you have 12/24 VDC power to your dimmer?

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
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