Bought a Lutron CL dimmer after googling around and seeing how easy it is to install a dimmer, but when I got home and took a look at my light switch I'm not sure its compatible?

The dimmer has 4 wires, but my light switch only has 2.

Here is the dimmer and the instructions: enter image description here enter image description here

But my light switch has only two wires which are both black. And one of the wire connects to a thumb screw, but the other one looks like it connects to that drilled in metal piece. enter image description here enter image description here

What do you guys think? Do I need an electrician, can I do it myself or is it just not compatible?

She works! I installed it upside down but hey it still works I'm happy. Special thanks to someguy obviously couldn't have done it without you. I was going to take a picture of it wired up but I forgot.

The wires were very thick copper so it was a little tricky to wrap the wires around them. For the green wire I had to completely remove the screw from the fixture, wrap the wire around it and screw it back in. enter image description here

Thanks again: enter image description here

  • Does this switch control multiple lights?
    – Tester101
    Commented Apr 8, 2015 at 14:05
  • No. I linked to this question from a new question I asked about using this same kind of dimmer to control multiple lights.
    – red888
    Commented Apr 8, 2015 at 14:06

2 Answers 2


This will work, or at least you can connect it.

Right now we will trust that it is the right dimmer for the lamps.

You have all you need, and if you have made it this far, you will be fine.

Adding to the confusion in this project is that the dimmer can be used for either a single pole switch, or a 3 way switch. (Kinda clever for sales, but frustrating where the directions are concerned.

Your switch has 2 wires, one to the light and one to power. 2 wires are the sign of a single pole switch. 3 wires are a sign of a 3 way switch.

The White wires, twisted together and tucked off to the left side in the pictures stay as they are, you will not do anything with them.

The Black wire, that right now goes to the lighting fixture, this is the wire that goes into the metal cable and is not connected to anything else.

This will get twisted together, clockwise fiwith the Red/White stripe wire, that came with the blue wire nut on it.

  • This gives you 2 wires twisted together under a blue wire nut. The Red/White stripe dimmer wire, and the Black wire that goes into the wall.

The other Black wire, the one that currently goes to the power/hot wires, these are the 4 Black wires that are twisted together under the red wire nut.

This will be combined with the Black wire, and the Red wire from the dimmer switch.

Remove the red wire nut from the black wires.

Untwist and remove the Black wire from the switch. This leaves 3 Black wires twisted together. The short piece of Black wire that you removed will not be used. It is now trash.

Twist the Black and Red wires, come from the dimmer together.

Take the wires you just twisted together, from the dimmer with the 3 Black wires, that are already twisted together. This does not have to hold together well, they can sit beside each other.

Take the red wire nut, that you removed earlier, and twist together the 5 wires. 2 from the dimmer and 3 that were already twisted together. The important things, the bare wires all touch, and you can not see any bare wire outside of the wire nut.

  • You now have 5 wires, 4 Black and 1 Red, connected under the wire nut.

There is 1 wire left not connected.

The green wire on the dimmer is ground. The switch box you are showing has, 'bx' type wire, it is metal and sprials around the copper wires. I am sure someone will kick my ass for saying this but here goes.

Bend the bare end of the green wire into a hook. Loosen up the screw at the top of the box that holds the metal cables in place. The put the ground wire hook around it, clockwise, so the end of the wire will be on your right. And tighten the screw back, keeping all the fiddly bits that were also being held down, as they were.

  • 1 Green wire, connected to the metal box.

You have:

4 White wires, topped with a red wire nut that you have not touched.

A Blue wire nut, with 1 Black and 1 Red/White stripe wire.

A Red wire nut, connecting 4 Black and one Red wire.

A Green wire screwed under a metal clamp, in the metal box.

A short bit of Black wire, that you removed and trashed.

Turn the power on - try your dimmer and please let me know what happens.


Great job on the posting, nice pictures, lots of details, makes it easy to answer :)

  • But how do I connect the wires? Do I unscrew the white and connect it to the green? And what about the 2 black ones they are the same color how do I know which ones they connect to?
    – red888
    Commented Mar 28, 2015 at 23:45
  • @red888 I think I have the answer finished. best of luck
    – Some Guy
    Commented Mar 29, 2015 at 1:10
  • 1
    threephase, yeah, the lack of a ground screw bothers me too. I would love to see a ring terminal on the ground, then screwed into the box. Up for any suggestions, please. Yes, my first round at the answer got the neutral completely wrong, more than a little embarrassing, much more, like flat out wrong. Thanks for keeping an eye on me.
    – Some Guy
    Commented Mar 29, 2015 at 1:21
  • 1
    The red with white stripe wire should not be used in a single pole installation. You should also not be connecting the black and red wires from the dimmer together.
    – Tester101
    Commented Apr 8, 2015 at 13:48
  • 1
    @red888 This answer has you wiring the switch like this. Notice how one of the switched wires loops back and connects to the wire supplying power to the switch. It won't make a difference, since both are at the same voltage potential. It's just not the way you're supposed to wire the switch.
    – Tester101
    Commented Apr 8, 2015 at 14:39

This is a single pole switch, so you should follow the single pole instructions in the installation guide.

Single Pole Dimmer Wiring


While you could remove the red twist-on wire connector, and use it to connect the black wire from the switch to the other wires. There's no reason to disturb the wires if you don't have to (and you don't have to). Just use the twist-on wire connectors provided with the switch, and attach the black wire to the wire that was attached to the old switch.

The red wire with a white stripe should not be connected to anything, when using the dimmer as a single pole device. Just leave the preinstalled twist-on wire connector in place, and tuck the wire into the box.

  • hmmm yes yes very interesting. Let me propose a hypothetical: suppose I am a lazy asshole and it already works the way I installed it (as per the accepted solution)... why should I open it up and fix it if it already works? Is there a possibility of an electrical fire or could I possibly be using extra electricity to power it? Because if not I ain't touch'in that mofo.
    – red888
    Commented Apr 8, 2015 at 14:29
  • 1
    @red888 You can do what you want, I'm just telling you the "correct" way to wire the switch (as per the installation instructions).
    – Tester101
    Commented Apr 8, 2015 at 14:43

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.