Replacing Single-Pole Switch with a Single-Pole Dimmer Switch


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Old 02-11-21, 02:06 PM
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Replacing Single-Pole Switch with a Single-Pole Dimmer Switch

Hello all,

I am new to this forum and full-disclosure, I am not an electrician. But unfortunately, I must fix some very minor things in the office provided it is safe and within my comfort level.

I am in the process of replacing my current single-pole switch with a single-pole dimmer switch. From my limited understanding:

1. Turn off the circuit breaker correlating with the switch I am replacing
2. Use a volt-meter to find which is the hot-wire
3. My new dimmer switch has a green wire (ground), black wire and red wire
4. The light switch box casing is plastic, with two (2) black wires screwed into the side on the switch, the green wire is screwed into the opposite side of the two (2) black wires
5. I switch my volt-meter to AC, and 200, I place the black lead on the green ground wire lead, and place the red lead on one of the black wires and look for a reading close to 120V

Issue:
1. Neither black wire on the switch show any reading, except one of them shows ".1"

I cannot find which is the hot wire here.

I can provide photos of the switch box wires should anyone wants to assist.
 
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Old 02-11-21, 02:35 PM
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Maybe I'm reading this wrong. In the order you listed, you shut off the power from the breaker, then try to measure voltage across wires and you're getting a reading. Is that correct? If it is then you have two hot wire circuits going into that box. You can't measure voltage with power off.
Yes please send pictures.
 
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Old 02-11-21, 03:30 PM
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Well I am an idiot. I forgot one step that I did. I removed the two black wires and the green ground wire form the light switch. Turned the power back on at the breaker, and then tested with my volt meter. And that is when I received the reading of .1

I will upload the pictures next.
 
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Old 02-11-21, 03:42 PM
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Did you already do this with the wires in the box all disconnected from the old switch?

Turn on the breaker.

Verify that meter is set to 200 volts AC

Measure between one black wire and the green wire.

Measure between the other black wire and the green wire.

Exactly one reading should be about 120 volts. Mark that black wire "hot"

Mark the other wire "load".

If you got something else, stop and describe what you got.

The new switch should be labeled with one wire or terminal as "hot" or "line" and another terminal as "load" or "light" or "switched". You would connect up the wires in the box to the matching switch terminals. Connect the green wire in the box to the switch terminal or wire labeled ground or green in color.

(In the future, do not unhook wires without first labeling them in a fashion that you could put it back the way it was.)



 
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Old 02-11-21, 03:56 PM
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Here are the pictures.








 
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Old 02-12-21, 02:40 PM
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Yes Thank you regarding labeling the wires.
Did you have a chance to look at the pictures? I went through your steps above, and I this time the reading went all the way up to 170+ on both black wires. Not even sure if that is possible.
I also used a small handy 120v test which just lights up if it sense ~120V and still nothing lit up on the small handy one.
Any other ideas?
 
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Old 02-13-21, 05:44 AM
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I am puzzled by 170 volts and at this moment do not have more ideas to try yet..One hundred seventy volts is definitely incorrect and out of place.
 
 

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