Please help if you can... I just replaced some old 3-way switches with new Maetro+Controller 3 way dimmers. I did this on 2 light separate lights (I.e. changed a total of 4 switches... 2 of these: Lutron MA-R-WH Maestro Companion 120V 8.3A Designer Digital Dimmer Switch and, 2 of these: Lutron Maestro C.L Dimmer Switch for Dimmable LED, Halogen & Incandescent Bulbs, Single-Pole or Multi-Location, MACL-153M-WH

I got the same behavior on both circuits. Here is the problem. When I was done wiring up, the lights looked a little dimmer than before (everything else worked perfectly). So, I measured the voltage at one of the 4 chandelier bulb sockets where I got a voltage to ground of 100VAC!!! Bizzar! There is only one light being controlled on each dimmer circuit (a chandalier with 4 small bulbs...I.e. low load). So, I measured the voltages along the circuit. Here is what I found:

  1. Power leg into first dimmer: 120V

  2. With the light turned on, the voltage on the same dimmer: 100V on one connection and 107V on the other (pretty sure the 107V is the phantom voltage).

    3.The voltage on both powered legs of the 2nd dimmer is 100V--I.e. 100V from the first transformer and 100V on the line to the light fixture (107V also on the secondary connection/fantom?).

As mentioned above, I have a second light that I also changed the switches on. Same power coming in and same neutrals. I got the same result. I disconnected the second one to see if it was impacting the first... it didn't seem to be).


Thank you in advance. Dave

Circuit schematic

  • Hello, and welcome to Home Improvement. How are you measuring these voltages? Note that generic voltmeters have a tough time with strange power waveforms such as dimmers put out. And, you should probably take our tour so you'll know how best to participate here. Feb 16, 2020 at 18:51
  • 1
    Why is this a concern for you? Is the loss of dimming range on the high-end causing you an issue? Feb 16, 2020 at 19:09
  • Dimmer Companion Feb 16, 2020 at 19:58
  • Noting that these are series-wired dimmers, have you tried replacing one bulb with incandescent? Does that help? Feb 16, 2020 at 20:12
  • How are you measuring this voltage exactly? Measuring dimmer output can be weird, because the output is not sine waves. Feb 16, 2020 at 20:19

1 Answer 1


It is KNOWN that you have a voltage drop across a dimmer,..even when turned up/on all the way. They could MFGR them so it is a true bypass when on all the way, but they do not. I assume it is to save a buck or two. The ones that are noticeable.....I usually take them back. I've had a few that were only letting 100 volts get by,...you ALWAYS notice it is dimmer at 100,.. and usually, even at 110. I think the decent ones loose about 5 volts only, and you can live with that. In the sound business, where you are trying to keep all frequencies under control evenly,..people actively seek out a potentiometer that has a true bypass of the internal circuit when it is turned all the way on...and they expect to pay extra (not much,..it's easy to do).,

  • 2
    Welcome to Home Improvement. With all the SHOUT CASE and lack of formatting, this feels more like a rant than an answer. Please take a minute to take the tour, then look through tips on how to answer then feel free to edit your answer.
    – FreeMan
    Oct 11, 2022 at 14:01

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