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Mike G.
Mike G., Master Electrician
Category: Electrical
Satisfied Customers: 5501
Experience:  Proven Professional 45 years Experience
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I have a light switch with three black wires and three white

Customer Question

I have a light switch with three black wires and three white white coming out of it. I want to put a dimmer on that outlet. The dimmer either has two black plus green ground for a single pole OR two red, one black plus green ground for a three pole which is my first choice as this new switch has a toggle and a lever to control the dimmer. How do I attach the dimmer to these wires? Unfortunately, I already removed the switch and don't remember which wire went where.
Help!
Submitted: 1 year ago.
Category: Electrical
Expert:  Steve G. replied 1 year ago.

Hello there and welcome to Just Answer. My name is XXXXX XXXXX I will be assisting you today. I am an engineer with over 30 years of electrical and electronic training, repair and installation experience. I will try and answer your question accurately and precisely so that we can get you on your way.

Is there just one switch in this box?

Do you have a voltmeter?

Please let me know so that we can continue.

Regards

Steve

Customer: replied 1 year ago.

Yes, this light is operated by only one switch and no I do not have a volt meter.

Expert:  Steve G. replied 1 year ago.

Does the light you are controlling have another switch - for example, on a staircase, you will have a switch at the top and one at the bottom that control the same light.

Please let me know so that we can continue.

Regards

Steve

Customer: replied 1 year ago.

NO, this is for an outside patio light that only has one switch controlling it. I had a single pole dimmer on it before with a simple slide mechanism. I now want to put a different dimmer on with a slide mechanism as well as an on/off toggle switch. This second dimmer happens to be a three pole. Will this work? If so, how do I go about finishing this mess I created?

Expert:  Steve G. replied 1 year ago.

Well, first, I'm trying to understand how you have more than two wires at your light switch - you have six!

When you pulled the original dimmer out of the box, were all six wires connected to it?

Customer: replied 1 year ago.

You and me both...This is a "grey" area for me too. I honestly don't remember. I do seem to recall the white wire were all bundled together and knotted off, there were two black ones that have similar paint spackle on them and one black one that is cleaner than those two.

Expert:  Steve G. replied 1 year ago.

Ok, the three whites are your neutrals and yes, they were probably wire-nutted together.

That leaves you with three wires.

We really need a meter or at least a voltage tester. You can get one for $10-$15 from Home Depot or Lowes. No knowing which of those is hot makes it nigh- impossible to figure out.

Steve

Customer: replied 1 year ago.

I have changed out numerous single pole switches to dimmers in the past but never encountered this. I usually don't turn off the breaker and just go for it. Having said that, I definitely know which is the hot black wire and which is not.


As I mentioned, two of the three black wires seem to have been twisted together at one point as they have a similar look of excess "spackle" from initial construction of our home. The other black is cleaner, but also in the same box.


The frustrating part is this was working fine WITH the single pole dimmer up until I had the bright idea to switch it out for a different dimmer with both the slider and toggle. Now it's either all on or all off and the only way to turn it of is to disconnect the wires.

Expert:  Steve G. replied 1 year ago.
Ok, so you know your hot wire. Can you pull the fixture and find out which wires are at the fixture?
Customer: replied 1 year ago.

No, not without removing the lantern which is higher up on the wall requiring a ladder. I just monkeyed around further and can tell you that the only combination this light comes on is when the two black similar wires touch each other.


What I want to accomplish is have the three pole dimmer installed so i can have both the toggle and slider option.


 

Expert:  Steve G. replied 1 year ago.

Ok, so the two blacks act as a switch? Touching those, lights the fixture?

Was one of those blacks the previously known hot wire?

Customer: replied 1 year ago.

Yes, the two blacks of similar appearance act as an on-only switch. I'm not sure if it was previously designated as the hot wire, but it certainly is now.

Expert:  Steve G. replied 1 year ago.

Ok, so we have a remaining black wire and we do not know if it is hot - or where it goes to.

Ok, is the S-603P the switch that you have there? That is a three way dimmer - but you do not have another switch location - correct? Why do we have the three way dimmer switch?

Please let me know so that we can continue.

Regards

Steve

Customer: replied 1 year ago.

Correct about the remaining black wire.


 


We've moved several times over the course of a few years and have always had dimmers of one kind or another. I was in the garage yesterday and came across some dimmers that I wanted to use in this application. They were not specially purchased for this project; I already had them. We used to have a home furnishings and interior design shop and always had dimmers around.


 


Yes, the S-603P is the three way dimmer and this particular light does NOT have another switch location.

Expert:  Steve G. replied 1 year ago.

Ok, so we can just use the dimmer as a 2 way, we just won't use the third wire.

So, let's wire nut off the remaining black wire for now. I have a feeling it may go t another light or receptacle bit for now, leave it disconnected.

Using the two wires that 'switch' the existing fixture on and off, connect one to the common and one to either one of the 'travelers', it doesn't matter which. Ideally, the hot wire should be connected to the common but it is not essential.

Try that and the fixture should be able to be dimmed and switched on and off.

Let me know if it does not. I'll be here.

Steve

Customer: replied 1 year ago.

Nothing!

Expert:  Steve G. replied 1 year ago.

Ok, so touching the two wires together turns the light on and off but wiring in the switch doesn't?

Are you sure that you are not connecting to both travelers? You need one of those wires to be on the common and the other on either of the travelers.

Please let me know so that we can continue.

Regards

Steve

Customer: replied 1 year ago.

honestly, i don't know what you mean about the "common" vs the "traveler" but i have tried numerous combinations during the time i was waiting for your replies. i have even tried two other dimmers to make sure the one i started with is functioning.

Expert:  Steve G. replied 1 year ago.

These other dimmers, are they also 603s?

Customer: replied 1 year ago.

Yes, those are the three pole and the others, the S600's, are the single....sorry, had a business call since we last corresponded.

Expert:  Steve G. replied 1 year ago.

No probs.

Ok, so you have two wires that when touched together send power to the light but when you put in a dimmer switch you get nothing?

Is the fixture fluorescent?

Customer: replied 1 year ago.

Sorry, I had Cox Communications on the phone with me forever fixing a connectivity issue.


 


No, this is a regular incandescent bulb.

Expert:  Steve G. replied 1 year ago.

Then I am at a loss.

If touching the two wires together turns on the lamp but wiring in a dimmer doesn't, I am stumped especially with the 2 way switches.

I am going to opt out of this question which will allow other experts to chime in.

Hold on.

Expert:  Mike G. replied 1 year ago.

Hi, I'm Mike and I'll be glad to assist you. I read the conversation with the previous expert and can only assume that you use ther red wire for connection to the house wires. That would cause exactly what you described. Use the black dimmer wire to the hot and the unknown black wire and one of the red dimmer wires to the black wire to the light. Cap the unused red wire. That should resolve the issue.

 

 

Mike G., Master Electrician
Category: Electrical
Satisfied Customers: 5501
Experience: Proven Professional 45 years Experience
Mike G. and 2 other Electrical Specialists are ready to help you
Customer: replied 1 year ago.

Mike,

Please recall the incident. Neither you or your counterpart could answer my electrical question which I eventually figured out myself through trial and error and I'm still not convinced I did the connection correctly.
I only hope that by trial and error, the error is not conducive to an electrical fire.

Doug

Expert:  Mike G. replied 1 year ago.
Please be more specific as to exactly what you did and how it differed from my directions.
Customer: replied 1 year ago.


You didn't give me any directions. Below is my original question along with your response. Had you read my question in advance, you would have seen that there are NO red wires coming out of the wall, however, your response is posted below mine.


 


My original question was this, "I have a light switch with three black wires and three white white coming out of it. I want to put a dimmer on that outlet. The dimmer either has two black plus green ground for a single pole OR two red, one black plus green ground for a three pole which is my first choice as this new switch has a toggle and a lever to control the dimmer. How do I attach the dimmer to these wires? Unfortunately, I already removed the switch and don't remember which wire went where."



Here is your initial response: "Hi, I'm Mike and I'll be glad to assist you. I read the conversation with the previous expert and can only assume that you use ther red wire for connection to the house wires. That would cause exactly what you described. Use the black dimmer wire to the hot and the unknown black wire and one of the red dimmer wires to the black wire to the light. Cap the unused red wire. That should resolve the issue."



To answer your recent follow up question, because I tried so many combinations to get this dimmer working, I don't recall what happened exactly. I have one of each of the black wires attached to one of each of the wires in the dimmer. My final combination allows me to dim the light and turn it on and off as normal. NONE of the wires got capped off. The three white wires in the wall that were capped when I opened it up remain as such.



Unless you are saying to do the same thing similar to what I have done, I don't understand your initial response. The only red wire that come into play at all are on the three pole dimmer switch.



Thank you...

Expert:  Mike G. replied 1 year ago.
The dimmer being a 3 day has a black feed and 2 red travelers. Using it as a single pole dimmer, you cap one of the red wires and nothing is connected to it. The 3 pairs of wires in the box should be a feed pair, a pair to the light and a pair that go to other outlets. The diagram I gave you shows how the dimmer should be wired with the information you gave.

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