If under cabinet LED lights stopped working, first determine whether the failure affects the entire system or only one section. A complete outage usually points to the switch, power supply, driver, dimmer, or an upstream connection. A dark or dim section within an otherwise working installation more often points to a loose connector, reversed polarity, damaged low-voltage wire, voltage drop, or failed LED strip.
Do not begin by replacing the strip lights. The most efficient approach is to isolate the fault from the supply toward the LEDs: confirm the control is on, identify the system type, check for power at the driver, then check the driver's output and each downstream run. Turn power off before opening junction boxes, moving wiring, or remaking connections. If the system is hardwired and you are not comfortable testing electrical equipment safely, ask a qualified electrician to diagnose the supply side.
Start by identifying the type of under-cabinet lighting
The troubleshooting path depends on what is installed.
- Plug-in low-voltage strip or puck lights: A wall receptacle powers an external driver or power supply, which sends low-voltage DC power to the LEDs.
- Hardwired low-voltage strip or bar lights: Household wiring supplies a concealed driver, often inside a cabinet, above cabinets, in a basement, or in another accessible location.
- Direct-wire LED fixtures: Each fixture connects to household power and has an integral driver. There may be no separate low-voltage power supply to find.
- Battery-operated or rechargeable lights: These use a different diagnostic path: check charging, batteries, sensors, and the fixture itself.
Look for a label on the strip, fixture, or power supply before disconnecting anything. It should identify whether the LED side is low-voltage DC and state the required output voltage. A replacement driver must match the lighting system's required output type and voltage; a driver is not interchangeable simply because its plug fits.
Use the symptom to narrow the likely cause
| Symptom | More likely causes | First checks |
|---|---|---|
| All lights are off | Tripped breaker, switched receptacle, failed wall switch, failed driver, dimmer issue | Check other loads, switch position, receptacle or driver input power |
| All lights flicker or pulse | Failing driver, overloaded driver, incompatible dimmer, loose supply connection | Bypass or set dimmer high if appropriate, inspect driver and connections |
| One cabinet run is dark | Loose connector, broken wire, reverse polarity, failed strip section | Inspect and reseat the connection at the dark run |
| Far-end LEDs are dimmer | Voltage drop, undersized wire, overly long run, power fed from one end | Compare brightness near and far from the driver |
| A short segment is dark while the rest works | Damaged LED strip, cut-point connection failure, local heat or physical damage | Test the affected strip with a known-good compatible connection |
| Lights work briefly, then turn off | Driver overload, overheating driver, thermal protection, intermittent connection | Let the system cool, check total connected load and ventilation |
1. Confirm the switch and supply power
Check the simple causes first. Make sure the wall switch, cabinet-mounted switch, touch control, motion sensor, or smart control is actually calling for the lights to turn on. Some under-cabinet systems have more than one control point.
For plug-in systems, test the receptacle with another known-working device. A receptacle can be switched, controlled by a GFCI device elsewhere, or affected by a tripped breaker. If a nearby receptacle works but the lighting receptacle does not, stop there and investigate the branch circuit rather than the LEDs.
For hardwired systems, do not assume a driver has failed because the lights are dark. The driver may not be receiving supply power. A qualified person can verify power at the driver's input with an appropriate tester or meter. If there is no input power, the problem is upstream: switch, dimmer, splice, circuit protection, or supply wiring.
Burn marks, melted insulation, a hot electrical smell, crackling, or repeated breaker trips are reasons to stop troubleshooting and arrange professional service. Do not reset a breaker repeatedly to keep testing a system.
2. Find the driver and inspect it before replacing it
A low-voltage LED driver converts household power into the DC power needed by many strips, pucks, and bars. It may be called a transformer or power supply, but its label provides the information that matters.
With power off, inspect the driver and nearby connections for:
- loose low-voltage terminals or plugs;
- damaged, pinched, or abraded cable;
- corrosion, especially near sinks or cleaning areas;
- discoloration, swelling, melted plastic, or an unusual odor;
- a driver hidden in a cramped location with little opportunity to shed heat.
A driver can fail without visible damage. It can also appear to work with no load but drop out when the lights are connected. If you are trained and equipped to use a multimeter safely, compare the driver's labeled output with the output measured according to the meter and driver instructions. A driver that has correct input power but no usable output is a strong replacement candidate.
Do not test a low-voltage output by touching wires together or by connecting an unknown fixture. A short circuit can damage the driver or wiring.
3. Isolate the downstream wiring and LED runs
If the driver output is present, work outward one run at a time. Disconnect and reconnect low-voltage plugs only with power off unless the equipment instructions explicitly provide another safe method.
Start with the first connector after the driver. Then inspect each splitter, extension lead, corner connector, strip-to-wire joiner, and connection between fixtures. Loose push-in connectors and poorly seated strip clips are common failure points. A connector can look intact while its metal contacts no longer grip the strip pads securely.
For tape light, check that the strip was cut only at its marked cut points and that connectors align with the copper pads. If a strip has positive and negative markings, polarity must remain consistent from the driver through every extension and connector. A reversed connection may leave a run dark and can cause problems in systems with multiple linked sections.
Where possible, use substitution to isolate the fault:
- Connect a dark strip or fixture directly to a known-working compatible output near the driver.
- If it lights, the original extension wire or connector is likely at fault.
- If it remains dark while a known-good strip works on that same output, the strip or fixture is likely faulty.
- If no runs work on a driver output that should be live, revisit the driver and its input-side controls.
Avoid cutting, stripping, or altering concealed wiring just to reach a conclusion. A clean test at accessible connectors is usually enough to identify whether the problem lies in the driver, cable, or lighting run.
4. Check for voltage drop when lights are dim at the far end
Under cabinet lighting voltage drop is most likely when LEDs nearest the driver look normal but those farther away are visibly dimmer, warmer in color, or less consistent. Voltage is lost along a run of low-voltage cable, particularly when the wire is too small for the distance and load or when many strips are fed in sequence from one end.
A failing connection can create a similar pattern, so inspect connectors before redesigning the wiring. If the dimming has been present since installation, voltage drop is more likely. If it appeared suddenly, a loose, corroded, or heat-damaged connection may be the more likely explanation.
Typical remedies include shortening the low-voltage run, using a heavier-gauge cable suitable for the system, dividing the lighting into separate runs, or feeding an appropriate strip arrangement from more than one point. The correct approach depends on the driver's output, the strip's voltage and wattage, cable length, and the manufacturer's permitted wiring arrangement.
Do not place low-voltage LED wiring into the same cable path as household-power wiring unless the product instructions and applicable local rules allow that arrangement. Verify current local requirements with a qualified electrician when wiring is concealed or being changed.
5. Consider the dimmer, sensor, or smart controller
A system that flickers, hums, turns on only at certain settings, or will not fully switch off may have a control compatibility problem rather than a bad strip. LED drivers can require a specific dimming method, and a dimmer that worked imperfectly from the start may eventually make the system seem unreliable.
If the lighting uses a dimmer or smart controller, check the driver label and manufacturer documentation for compatible controls. If an accessible compatible bypass test is possible, removing the controller from the low-voltage path can help identify it as the fault. Do not improvise a bypass on hardwired household-power connections.
For more on symptoms linked to controls, see our guide to LED lights that flicker after installing a dimmer.
When to replace the driver, strip, or entire system
Replace the driver when it receives proper input power but does not provide the specified usable output, when it repeatedly shuts down under a normal load, or when it shows physical signs of overheating or damage. Match output voltage, output type, dimming method if used, connector arrangement, and sufficient capacity for the connected lighting. Do not choose by wattage alone.
Replace the LED strip or fixture when a known-good driver and connection power other runs normally but that strip remains dark, has failed segments, or has damaged pads or conductors. In older tape-light installations, replacing a whole continuous run is often more reliable than patching several failing sections.
Replace or substantially rebuild the system when the driver is inaccessible, multiple strips and connectors have deteriorated, the layout suffers from persistent voltage drop, or the parts no longer have compatible replacements. This can be a sensible opportunity to improve driver access and use a simpler wiring layout. Our under-cabinet lighting installation guide explains the planning considerations for a replacement system.
Call an electrician when the problem is on the supply side
A homeowner can often inspect accessible low-voltage plugs and replace a matching plug-in driver or strip according to the product instructions. Bring in a qualified electrician when the failure involves hardwired supply wiring, a junction box, a breaker that trips, a failed wall control, concealed cable damage, or uncertainty about the system's wiring method.
Also get professional help if the driver is inaccessible behind finished surfaces. Drivers and electrical connections should remain serviceable; burying a replacement in a wall or cabinet cavity can turn a straightforward future repair into a larger one.
A short prevention checklist
- Keep the driver accessible and avoid enclosing it where heat can build up.
- Use connectors intended for the exact strip or fixture type.
- Support cables so they are not pulled tight, pinched by cabinet parts, or exposed to damage.
- Size the driver and wiring for the actual connected lighting load and run length.
- Verify dimmer compatibility before changing controls.
- Test every run before closing cabinet panels or concealing wiring.
If the lights are newly installed but have never been equally bright, review placement and wiring layout as well as troubleshooting. The guide to where to mount under-cabinet LED strips can help distinguish a lighting-layout issue from an electrical fault.
References
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- Troubleshooting — LED Cabinet Lighting. (n.d.). https://www.ledcabinetlighting.com/troubleshooting
- Placement options for under cabinet lighting. (n.d.). https://pdf.lowes.com/productdocuments/5cbe0368-4e38-4cce-a864-c350883d1286/11511530.pdf
- Where to Install LED Drivers for Easy Maintenance. (n.d.). https://brightnexled.com/blogs/led-resources/where-should-led-drivers-be-installed-for-easy-maintenance
- Electric Under Cabinet Lighting: Troubleshooting Issues in .... (n.d.). https://www.paclights.com/explore/electric-under-cabinet-lighting-troubleshooting-issues-in-electrical-lighting-systems
- Under Cabinet Lighting Wiring: Methods, Types & NEC Requirements | Ampora - Electrical Calculator & AI Assistant. (n.d.). https://amporalabs.com/blog/under-cabinet-lighting-wiring
- Cannot find power source for under cabinet lights.. (n.d.). https://www.reddit.com/r/electrical/comments/14ct0l2/cannot_find_power_source_for_under_cabinet_lights
