Why Does My Leviton Decora Smart Dimmer Flicker Only After Sunset

Problem Description

Some Leviton Decora smart dimmer users report flicker only after sunset, with no issue during the day. This guide explains how grid load patterns, LED driver behavior, and scene triggers combine to create evening-only flicker.

Why This Happens in Real Homes

Flicker that shows up only after sunset is a clue, not a coincidence. In most cases the lights are being driven to a low brightness in the evening — often by a sunset-triggered scene or schedule — and that low level lands right in the dimmer's flicker zone, where LED bulbs struggle to hold a steady output. During the day the lights are off or at full, so the problem never appears.

Check your automations first: find the sunset scene or schedule and see what dim level it sets, then either raise that level or raise the dimmer's low-end trim so the evening brightness stays above the flicker zone. Two secondary factors reinforce the pattern — evening is peak-demand time on the grid, so line voltage can sag slightly, and flicker is simply more visible in a dark room. Compatible LED bulbs and a tuned trim make the dimmer far less sensitive to those small dips, so the evening flicker stops.

Symptoms

• Flicker only after sunset
• No flicker during the day
• Evening-only flickering
• Starts when lights come on at night
• Flicker with a sunset schedule
• Worse in the evening
• Fine by day, flickers at night
• Flicker tied to a scene trigger

Recognize these? Here's what usually causes it.

Common Causes

• A sunset scene/schedule setting a low dim level in the flicker zone
• Low-end trim too low for evening use
• Evening grid voltage variation (peak load hours)
• Incompatible LED driver more visible in the dark
• Load below the dimmer's minimum at low levels
• Scene/automation dimming to a problem percentage
• Mixed bulbs flickering at low output
• Firmware out of date

Tools & Requirements

Step-by-Step Solution

1

Measure Voltage Day vs Night

Use a multimeter at a nearby outlet on the same branch circuit. Measure voltage midday and again after sunset. If evening voltage drops 5V or more, grid-related sag is making the LED drivers marginal at lower dim levels. Document readings for later comparison.

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Klein Tools 80196 Digital Multimeter Kit with C...

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2

Try Known-Good LED Bulbs

Replace the bulbs with premium LED lamps rated for dimming and listed on the Leviton compatibility sheet. Many evening-only flicker reports trace to cheap drivers that fail under both dim command and grid sag simultaneously. Premium drivers are far more tolerant.

3

Raise Evening Minimum Dim

In the Leviton app, raise the scheduled evening dim level to at least 30 to 40 percent. If scenes drop below the driver minimum during voltage sag, flicker is guaranteed. A small lift eliminates flicker without significantly changing the visual ambiance.

Needed for this step

Neoteck Non-Contact AC Voltage Tester Pen, AC 1...

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4

Audit Triggers

Check for motion triggers, geofence events, or scene transitions that fire near sunset. Rapid ramp commands from overlapping automations can make flicker appear evening-specific. Consolidate automations so only one commands the dimmer during the evening window.

5

Inspect Neutral and Update

Verify neutral connections at the panel and in the switch box are tight and free of browning. A poor shared neutral in branch wiring can manifest evening-only when other loads increase. Finally, update Leviton app and dimmer firmware and retest two evenings.

Quick Solutions

Still having issues? This is usually the deeper cause below.

Need More Help? Leviton Support

Note: The contact information below connects you directly to Leviton's official customer support team, not Trunetto. They can help with warranty claims, device replacements, and advanced technical issues.