Nine times out of ten it is not the lights. It is a mismatch between the dimmer, the LED driver, and the tape or fixtures, and the single most common version I find in Naperville kitchens is a brand new LED run wired to a dimmer that was built for incandescent bulbs.

That old dimmer needs a minimum load to work correctly, often 40 watts or more. A twelve foot run of under-cabinet tape might draw twenty. The dimmer never sees enough load to stabilize, so it stutters at the low end, flashes when you touch the slider, or refuses to turn all the way off.

I am Alexandr Godonoaga. I own Cob Services LLC and hold Illinois electrical license #26-00032356. I have spent more than ten years wiring kitchens in Naperville and the western suburbs, and under-cabinet flicker is one of the two or three calls I get most often after somebody else’s remodel. Here is how to figure out which version of the problem you have.

First, rule out the one that is actually dangerous

Before you blame the dimmer, check whether anything else in the house is flickering.

If lights in other rooms dim or pulse at the same time, especially when a large appliance cycles on, stop reading and call an electrician. That pattern points to a loose neutral, a failing service connection, or a bad lug in the panel, and it can start a fire. It is not a dimmer problem and no amount of swapping switches will fix it.

Inside Naperville city limits, the utility side of that is the city’s own Department of Public Utilities Electric division rather than ComEd, which is worth knowing when you call. In Lisle, Aurora, Plainfield, or Downers Grove you are on ComEd. Either way, get someone out. We do emergency electrical service for exactly this reason.

If the flicker is limited to the under-cabinet run, it is almost certainly a compatibility issue and the rest of this article applies.

The six causes I actually find, roughly in order

1. An incandescent-era dimmer left in the box

This is the big one. A remodel replaces the fixtures and keeps the switch, because the switch looks fine and nobody thinks about it. The old rotary or slide dimmer was designed to chop the waveform feeding a resistive filament, and an LED driver is not a filament. It draws a fraction of the current and behaves like a capacitive load.

Symptoms: flicker or flashing at the bottom of the dimming range, a dead zone in the last twenty percent of travel, buzzing from the switch box, or lights that pop back on at full brightness for no reason.

Fix: an LED-rated dimmer matched to your driver. Not “an LED dimmer” generically. A specific one from the compatibility chart, which brings us to the next item.

2. Forward phase where the driver wants reverse phase

Dimmers come in two flavors. Forward phase, also called leading edge or TRIAC, is the older design and is what most cheap LED-rated dimmers still are. Reverse phase, also called trailing edge or ELV, cuts the back half of the waveform instead and is much gentler on electronic drivers.

Most low-voltage LED tape runs on an electronic driver, and most electronic drivers want reverse phase. Put a forward phase dimmer in front of one and you get flicker, audible buzz, or both.

The industry standard that governs the forward phase side of this is NEMA SSL 7A, published by the National Electrical Manufacturers Association. It is worth knowing that the standard covers forward phase dimming only. It does not apply to reverse phase ELV or 0 to 10 volt dimming, which is exactly the category most under-cabinet tape falls into. So “SSL 7A compliant” on a box does not mean your tape will behave.

What actually works is the manufacturer’s compatibility list. Every major dimmer maker publishes one. The EPA says the same thing in its guidance on choosing dimmable lighting: check the dimmer manufacturer’s site for which products they recommend, and check the product packaging for recommended dimmers before you buy either one.

3. The driver is not dimmable, or it is loaded wrong

Two separate failures that look identical.

Some under-cabinet kits ship with a constant voltage driver that is not dimmable at all. Wire it to a dimmer and you get flicker across the whole range, or full brightness and nothing else. Read the driver label, not the tape packaging.

The subtler version: the driver is dimmable but underloaded. A 96 watt driver running 18 watts of tape is running at under twenty percent of capacity, and a lot of drivers get unstable down there. I aim to load a driver to somewhere between half and eighty percent of its rating. That leaves headroom without leaving it starved.

Oversizing the driver “to be safe” is one of the most common self-inflicted causes of flicker I see on homeowner installs and on jobs done by general remodelers who subbed the lighting to whoever was cheapest.

4. Mixed fixture types on one dimmer

Recessed cans, pendants over the island, and under-cabinet tape are three different loads with three different driver designs and three different dimming curves. Put them all on one dimmer because it made the switch plate look cleaner, and one of the three will misbehave.

They also will not track together visually. At fifty percent the cans look half lit and the tape looks nearly off, because dimming curves are not linear and are not standardized between manufacturers.

Separate dimmers for separate fixture types. It costs a little more in devices and box space and it is the difference between a kitchen that looks designed and one that looks assembled. When we lay out a kitchen we plan the switching alongside the fixture plan, which is part of what our custom lighting installation work covers.

5. No neutral in the switch box

This one is specifically a Naperville problem, or more precisely a problem with the housing stock here.

A lot of homes built before the mid-1980s were wired with switch loops, meaning the switch box has a hot and a switched leg and no neutral conductor at all. Older dimmers were built for that. They powered themselves by leaking a tiny current through the load, which an incandescent bulb absorbed without lighting up.

An LED driver does not absorb it. It converts it. So you get the classic symptom: the under-cabinet lights glow faintly when the switch is off, or blink slowly like a heartbeat.

The fix is either a dimmer that does not require a neutral and is specifically rated for LED loads, or pulling a neutral to the box. Which one makes sense depends on whether the wall is open. If you are already in a remodel, pull the neutral. It is cheap while the drywall is off and expensive afterward. If your house has this pattern in the kitchen it almost certainly has it everywhere, which is worth knowing before you start buying smart switches. Our wiring updates page covers what that work looks like.

6. Loose connections and long runs

Less common but worth checking. A backstabbed device, a poorly made splice inside a cabinet, or a wire nut that never got twisted down will produce intermittent flicker that comes and goes with temperature or vibration. Slamming a cabinet door and watching the lights blink is a diagnostic, not a coincidence.

Separately, 12 volt tape over a long run loses voltage along its length. The far end goes dim, and at low dimmer settings it can drop out entirely. Twenty four volt tape tolerates longer runs, and feeding a run from both ends helps. If your installer used 12 volt tape on an eighteen foot cabinet bank from a single feed point, that is a design problem rather than a dimmer problem.

What I check, in what order

When I walk into a flickering kitchen, this is the sequence:

Does anything else in the house flicker? If yes, the investigation moves to the panel and the service.
What is the dimmer, and is it rated for LED?
Is it forward phase or reverse phase, and which does the driver want?
What is the driver’s wattage rating versus the actual connected load?
Is the driver dimmable at all?
Is anything else sharing the dimmer?
Is there a neutral in the box?
Open the devices and check the terminations.

It takes about half an hour to work through in most kitchens. Most of the time it ends at step two or three, and the repair is a dimmer swap plus confirming the pairing against the manufacturer’s list.

Line voltage dimming versus dimming the driver

Worth understanding if you are specifying a kitchen from scratch rather than fixing one.

Line voltage dimming means the dimmer sits on the 120 volt side, chopping the waveform before the driver ever sees it. It is simple, it uses a normal wall device, and it is where nearly all compatibility trouble lives.

Driver-side dimming means the driver receives a separate control signal, usually 0 to 10 volt, and handles the dimming itself. It costs more up front. It also dims smoothly to very low levels without the flicker and dropout that plague phase-cut dimming, and it does not care what brand of tape you bought.

For a kitchen where the under-cabinet lighting is meant to work as low ambient light at night, not just task light at full output, I think the driver-side approach is worth the money. That is an opinion, not a code requirement, and plenty of good kitchens use phase-cut dimming without complaint. But if you are the kind of person who is going to notice a slight shimmer at ten percent, spend the extra.

One more spec worth asking about: PWM frequency. Inexpensive drivers pulse the LEDs at a low frequency to dim them, and while your eye may not catch it directly, it will show up on phone video and it gives some people headaches. Look for drivers advertised as flicker free or specified above about 1 kHz.

Does fixing this need a permit in Naperville?

A permit is required before electrical work begins inside Naperville city limits, and the city also requires the electrician to be registered as an Electrical Contractor with it. Swapping an existing device for a comparable replacement is generally treated differently than new work, but if the fix involves pulling a neutral, adding a circuit, or relocating a driver, that is permitted work.

We pull the permit in our contractor name when the job needs one. It is not the part of the job anyone wants to think about, and it is the part that stalls a project when it gets skipped.

While the walls are open, this is also the moment to confirm the rest of the kitchen circuit plan is right, because Naperville enforces the 2023 NEC and the kitchen requirements changed meaningfully in that cycle. Kitchen branch circuits need arc fault protection and the receptacles need ground fault protection. If a previous remodel added under-cabinet lighting by tapping a countertop circuit, that is a code problem sitting behind your backsplash. Our dedicated circuits page covers how those runs should be separated, and if the panel is out of space, the panel upgrade page covers that side.

Frequently asked questions

Why do my LED lights flicker when dimmed but not at full brightness? Almost always a dimmer and driver mismatch. At full output the driver draws enough current to stay stable. As you dim, the current drops below what the dimmer needs to regulate properly and the output becomes erratic. An LED-rated dimmer matched to your specific driver fixes it.

Why do my under-cabinet lights glow when the switch is off? Usually a dimmer that does not require a neutral, powering itself through leakage current that the LED driver converts into a faint glow. Common in Naperville homes wired before the mid-1980s, where the switch box has no neutral. Either install a dimmer rated to handle it or pull a neutral to the box.

Can I just buy an LED dimmer at the hardware store? Sometimes it works. Often it does not, because “LED compatible” on the package does not tell you whether the device is forward phase or reverse phase, and your driver cares. Check the dimmer manufacturer’s compatibility list against your actual driver model before buying.

Is flickering LED lighting dangerous? Flicker confined to one fixture group is a compatibility annoyance, not a hazard. Flicker across multiple rooms, or flicker that coincides with appliances starting, can indicate a loose neutral or failing service connection and needs to be looked at immediately.

Will a smart dimmer fix the problem? Not by itself. Smart dimmers have the same phase-type and minimum-load constraints as ordinary ones, plus most of them require a neutral. Swapping to a smart device in a switch box with no neutral usually makes the ghosting worse.

Why do my recessed cans and under-cabinet lights look different at the same dimmer setting? Different drivers follow different dimming curves, and those curves are not standardized between manufacturers. Putting mixed fixture types on one dimmer guarantees they will not track together. Separate them.

Do I need to replace the LED tape? Rarely. In most kitchens I see, the tape and driver are fine and the dimmer is wrong. Confirm the compatibility pairing before anyone sells you new fixtures.

Get it looked at properly

If your under-cabinet lighting has been flickering since the remodel and the contractor who installed it has moved on, call (630) 427-5923 or request service online. We will identify which of the causes above you have and tell you what the repair costs before we start.

If you are still in the planning stage, the better move is to get the switching and driver selection specified correctly the first time. That is part of what we handle on every kitchen and remodeling electrical job. You can see finished work on our recent projects page.

We work in Naperville, Aurora, Lisle, Plainfield, Bolingbrook, Downers Grove, Hinsdale, Burr Ridge, La Grange, Oswego, Lockport, Joliet, and Western Springs.

About the author

Alexandr Godonoaga is the owner and CEO of Cob Services LLC and an Illinois-licensed residential and commercial electrician with more than ten years of field experience in Naperville and the western suburbs. Illinois license #26-00032356. He walks every estimate personally and stays the point of contact through final inspection.

Connect on LinkedIn: Alexandr Godonoaga

Cob Services LLC 2020 Calamos Ct Suite 200, Naperville, IL 60563 (630) 427-5923 Monday through Friday, 9:00 AM to 5:00 PM License #26-00032356

Call: (630) 427-5923