Installing a Dimmer Switch: Here's What I Did

⚠️ Read this first: I am not a licensed electrician, and this post is not a how-to. It is a record of what I did at my own house, with my own wiring, and it should not be treated as instructions for your home. Electrical work can cause fire, serious injury, or death. If you are considering a project like this, please hire a licensed electrician.

I had two light switches side by side that didn't match — a standard toggle and an old twist-knob dimmer, on separate circuits. I replaced both with rocker dimmers so the wall would look like one intentional thing. The part of my job that surprised me wasn't the wiring. It was that in both boxes, the hot wire turned out to be white rather than black. That's the thing I most want to pass along, and it's the reason I had an electrician's work in mind the entire time.

Quick Facts

  • Project: What I did to replace two light switches with rocker dimmer switches
  • Difficulty: Live electrical work — for most homeowners this is a hire-it-out job, and I won't pretend otherwise
  • Time: It took me roughly 1–2 hours for two switches
  • Main challenge: Two separate circuits in one spot, and wire colors that didn't match their function
  • Best for: Reading before you call an electrician, so you know what questions to ask
  • Call a professional when: Honestly, for this one — and especially if you can't confidently identify a hot wire, if there's no ground in the box, or if anything inside looks modified or unfamiliar

The Situation

Two switches, right next to each other, with nothing in common visually. A traditional toggle on one side, and on the other one of those old round knob dimmers you twist. The knob one was genuinely old.

They control different things, and they sit on separate circuits — which mattered a great deal more than I expected it to.

I wanted both replaced with rocker switches that have dimmers built in, so the wall would stop looking like two decades of whatever was on hand. The switches I bought were around ten dollars each.

⚠️ Before You Start

I want to be as clear as I can here, because this is the one subject where I don't think a video or a blog post is a substitute for a professional.

I'm not a licensed electrician. I have no trade training. What follows is a description of what I did in my own home, on wiring I could see and test — not a procedure I'm recommending to anyone. If you aren't completely certain you understand every part of what you're looking at inside your own wall, the right answer is to hire someone. It genuinely isn't worth it.

Three things from my particular job that I think are worth knowing even if you never pick up a screwdriver:

My two switches were on separate circuits. Shutting off one breaker told me nothing about the other. I tested each one independently before touching anything, and I'd be nervous about anyone who didn't.

Wire color did not indicate function in my house. In both of my boxes, the white wire was the hot. That can be a legitimate configuration, but it means anyone assuming black-equals-hot would have been assuming wrong in my walls. Testing was the only thing that told me the truth.

Neither switch had a ground landing on it when I opened them up — just two grounds sitting in the box. I pigtailed off those to ground both new switches. I said on camera that I'd welcome an electrician's view on that setup, and I meant it. If you're qualified and you have a correction, I want to hear it.

What I Used

On the lever-style connectors: these are the ones where you lift a small lever, insert the wire, and close it. They cost more than wire nuts, and for making a pigtail off multiple grounds they made my life considerably easier.

What I Did

Everything in this section describes my own job in my own house. It is not a sequence I'm suggesting anyone follow.

1. Turned off both breakers. Two switches, two circuits, two breakers — I found both and flipped both off.

2. Removed the wall plate. The knob on the old dimmer had to pull off before the plate would clear. Then a thin flathead to back out the plate screws.

3. Verified zero volts at each switch, separately. Multimeter probes on the screws. Zero on the right-hand switch, then a completely separate check on the left-hand switch.

This is where I'd stop and call someone if I weren't confident. Confirming one switch is dead proves nothing about the one beside it when they're on different circuits, and a multimeter is only useful if you genuinely know how to read it.

4. Backed both switches out of the box. Two set screws each, into the blue box. I tested again once everything was pulled out and accessible.

5. Looked at how the first switch had been wired. This one was a 3-way.

The white wire was landed on the common terminal, which made it the hot — even though by color it "should" have been black. The black wire sat on one brass terminal, and the red was on the other as the traveler.

6. Made two ground pigtails. Two grounds in the box, nothing landing at the switches. I used a four-port lever connector, cut two six-inch pigtails of 14-gauge wire, and put it all in together — one pigtail out to each new switch.

This is the part of my setup I'm least certain about, and the specific thing I asked electricians to weigh in on.

7. Marked the white hot wire with black tape. A few wraps where it's visible. My understanding is that this is the conventional way of flagging a white conductor being used as a hot, and I wanted the next person who opens that box to have better information than I started with.

8. Read the instructions that came with the dimmer. These particular dimmers work as either single pole or 3-way, so the terminal assignments mattered. The instructions said hot goes to the black screw and the two remaining wires go to the red screws.

Every dimmer is different. Mine told me what it wanted. Yours will say something else.

9. Wired the first switch. Hot — the taped white — to the black screw. Black and red to the red screws. Ground pigtail to the green.

I hooked each 14-gauge wire with the needle-nose pliers and snugged the screws with the drill.

10. Tested before closing anything up. Power back on, carefully, and I checked that the switch worked and the dimmer swept properly. It did. Then power back off.

11. Opened up the old knob dimmer. No ground, and two wires of the same color coming out of the back — so I had no way to tell which was hot by looking at them.

Wing nuts off carefully, multimeter check to confirm zero, then the old dimmer came out.

12. Powered back on to identify the hot. With the wires separated and accessible, I turned the breaker back on and put the multimeter on them. One read 124 volts. Again, it was the white.

⚠️ This is live testing, and it is the most dangerous thing I did in this entire project. I'm describing it because it's what happened, not because I think it's a reasonable thing to ask a homeowner to do. If you reach this point in your own box and you aren't completely confident, this is the moment to stop and call an electrician.

13. Powered back off, taped the hot, and looped both wire ends. Black tape around the white, then hooked both ends with the needle-nose pliers.

14. Wired the second switch as a single pole. Nothing else in the room controls this circuit. Hot to the black common screw, ground pigtail under the green screw, the remaining wire to the other side.

One quirk with these particular switches: the terminal screws back all the way out and drop if you point them upward. I ended up tilting the switch so gravity held each screw while I hooked the wire around it.

15. Snugged with the drill, then verified every terminal by hand. The drill gets things tight quickly, but it can also leave a connection that only feels tight. I went back over each terminal with a regular screwdriver.

16. Tested the second switch with power on, confirmed it worked, then powered back off again.

17. Tucked everything in and buttoned it up. Wires folded back carefully so nothing pulled loose or stripped, switches secured with the provided screws, plate on and centered.

For the wall plate I used a hand screwdriver rather than the drill, so I wouldn't chew up the paint around it.

18. Powered both circuits back on for the final test. Both switches worked, both dimmers swept smoothly.

Prefer to watch?

Here is the video on YouTube.

The Result

Two matching rocker dimmers where there used to be a toggle and a twenty-year-old knob.

The left switch runs the kitchen lights as a 3-way, with its partner across the room. The right one is its own single-pole circuit. Both dim properly, and the rocker action feels solid rather than loose — which, at ten dollars a switch, I didn't expect.

A Note on "Your Setup Will Probably Be Different"

Mine was two switches on two separate circuits, one wired as a 3-way and one as a single pole, in boxes where grounds were present but not landed at the switches, and where white conductors were serving as hot in both.

Yours will almost certainly be different, and that's the entire reason I won't present any of this as instructions. The terminal assignments I used are mine. They describe my wall, not yours, and the only person who can tell you what's behind your own plate is someone qualified who is standing in front of it.

Two other things I came across that are worth asking an electrician about. Most dimmers aren't rated for 3-way at all, and in a 3-way pair you generally use one dimmer and one companion switch rather than two dimmers. And if you're running LED bulbs, dimmer compatibility is its own subject — not every dimmer works well with every LED, and the symptom is flicker or buzz at the low end of the range.

🧠 Homeowner Intelligence

💰 What I saved doing this myself: The switches were around ten dollars each and I already owned the tools. So $20 total. An electrician's minimum service call would have cost more than the parts did — though I'd point out that for a lot of people that charge is the correct purchase, not the avoidable one.

Why this matters (not just the steps): The lesson of my job is that the wire colors lied, twice. White was hot in both boxes. There's a version of this project where someone opens the wall, assumes black is hot because that's what everyone says, wires it accordingly, and creates a hazard that doesn't announce itself for years. That's the single best argument I know of for having someone qualified do this work.

Trickiest part of this specific install: Having to turn the power back on to identify the hot wire in the second box, because both conductors were the same color. That's live testing, and it's the step I'd most readily hand to a professional if I were doing it again.

How to know you're doing it right: In my case it meant zero volts at each switch independently before touching anything, every terminal verified by hand rather than trusting the drill, the switch tested and working before the plate went on, and the dimmer sweeping its full range without cutting out or buzzing.

When to stop and call an electrician instead: If you can't confidently identify which wire is hot. If there's no ground anywhere in the box. If the wiring looks modified, spliced oddly, or doesn't match anything you recognize. If you're not comfortable with a multimeter. And frankly, if you're on the fence at all — none of those is an embarrassing reason, and an electrician will have this done in less time than it took me.

What I'd do differently next time: Label the second box before pulling the old dimmer out. Two same-colored wires and no record of which went where is what forced me into the live test. A piece of tape and a pen beforehand would have made that step unnecessary.

Before You Wrap Up

✓ What I checked before I called it done: Both breakers back on, both switches working, every terminal hand-verified for tightness, wires tucked without strain, plates centered and not over-tightened.

💰 Where the money went: Two switches at roughly ten dollars each, plus connectors I'll reuse. The multimeter was the purchase that mattered most, and it's the one thing I'd call essential for anyone who's going to open a wall at all — including just to look before an electrician arrives.

➜ Watch next: Check out more videos in our DIY Electrical & Smart Home Upgrades playlist.

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⚠️ This post is a personal account, not instructions, and not a substitute for professional advice. I am not a licensed electrician or contractor, and nothing here should be treated as guidance for work in your own home. Electrical work can cause fire, serious injury, or death. Wire colors do not reliably indicate function — mine did not. Please hire a licensed electrician for switch, outlet, and fixture work. This channel is not liable for any damage, injury, or loss related to anything shown here, and any action you take based on this video or post is entirely at your own risk.