Owners describe a pattern of lighting defects across the 2016 Sonata that creates genuine safety hazards. Headlights cut out randomly while driving, sometimes triggered by engaging the turn signal or switching from high to low beam. One owner had lights drop repeatedly between 45–60 mph on a highway; others report lights turning off at night without warning and returning on their own or only after manipulating the turn signal lever back and forth. A few vehicles show a deformed headlight housing on the Limited trim that casts a dark shadow roughly 30–40 feet in front of the car, blocking visibility where pedestrians would be walking.
The turn signal stalk itself is faulty on some vehicles—engaging it causes headlights to flicker, turn off, or cycle through auto/on/off modes without driver input. Interior dome and reading lights activate on their own while driving or at startup, unable to be diagnosed or fixed by dealerships despite multiple service visits.
Brake and tail lights fail repeatedly; one owner replaced a bulb only to see both taillights fail again within three weeks. More alarming, several owners report burning smells, smoke, and melted wiring harnesses. One dealer diagnosed a melted harness after a burning odor but didn't repair it. Another owner has had interior lighting fuses melt repeatedly—a potential electrical fire hazard the dealer cannot resolve.
Hyundai's recall 21V749000 for exterior lighting was issued, but appointment delays stretched to two months or longer. Dealers often deny there's a problem or claim the lights meet factory specs despite acknowledging safety concerns.
Failure modes owners describe
Headlights turn off during operation (intermittent)
Headlights randomly shut off while driving, especially when engaging turn signal or switching between high and low beam. Owners report lights cutting out completely and returning on their own or after manipulating the turn signal lever. This is a known issue across multiple owners and has been compared to similar complaints online.
When: 35,000–95,000 miles; some occurring within weeks of purchase
Symptoms owners cite: Headlights randomly turn off while driving at night; Lights cut out when turning signals engaged; Lights cut out when switching from high beam to low beam; Lights flicker or cycle between auto/on/off modes; Headlights come back on after manipulating turn signal lever; Lights shut off for extended periods creating visibility hazard
Repairs/costs cited: Owners report no successful dealer repairs; one narrative mentions melted wiring harness diagnosed at dealer but not repaired
Recalls/TSBs owners mention: NHTSA Campaign Number 21V749000 (Exterior Lighting, Electrical System) issued but with long wait times for appointments; some dealers claim lights are within manufacturer specifications; no other recalls mentioned by owners
Defective headlight beam pattern (dark shadow/shadow casting)
Driver-side headlight produces a pronounced dark shadow across the center of the projected light beam, blocking illumination in front of the vehicle. This defect is confined to Limited trim headlight assemblies, which have the top edge of the housing cut off compared to non-Limited versions. The housing deformation prevents proper light projection.
When: Present in used and new vehicle purchases; noticed immediately or early in ownership
Symptoms owners cite: Dark shadow approximately 30–40 feet in front of vehicle; Light beam does not properly illuminate roadway; Headlight housing visibly deformed; Left (driver-side) headlight predominantly affected; Problem specific to Limited trim models
Repairs/costs cited: Owners replacing headlight assemblies privately; dealer confirmed deformation but did not cover repair
Recalls/TSBs owners mention: No recall issued; dealers state lights meet manufacturer specifications despite acknowledging the safety issue
Turn signal switch malfunction (affecting headlight control)
Turn signal lever is malfunctioning, causing unintended switching of headlight modes and random on/off cycling of headlights. When turn signal is engaged, headlights may turn off, flicker, or cycle through auto/on/off settings without driver input. High beam function can activate unexpectedly when turn signal lever is moved vertically.
When: Occurring over months of ownership; one complaint notes issue within weeks of October 2016 purchase
Symptoms owners cite: Turn signal engagement causes headlights to turn off; Lights flicker or cycle modes when turn signal activated; Touching turn signal lever causes light flickering; High beams flash on and off when right turn signal engaged; Light mode changes from auto to on to off without driver action; Auto lights do not engage properly when wipers activated
Repairs/costs cited: No repairs documented in narratives
Recalls/TSBs owners mention: Prior turn signal recall mentioned in one narrative; NHTSA Campaign 21V749000 applies but repairs delayed or unavailable
Interior lights turning on randomly
Interior dome and reading lights activate on their own without driver input. Lights may turn on while driving or at startup. Button depression temporarily stops the lights, but they engage again without the button being pressed. Problem affects driver-side, passenger-side, and rear interior lights.
When: Starting about 1 week after vehicle purchase; ongoing issue documented in maintenance records
Symptoms owners cite: Interior driver-side lights activate randomly; Interior passenger-side lights activate randomly; Interior rear lights activate randomly; Lights engage while driving and at vehicle startup; Lights cannot be replicated or diagnosed
Repairs/costs cited: No resolution found despite multiple dealer service visits
Recalls/TSBs owners mention: Issues reported to Hyundai manufacturer and dealership with no resolution offered; documented in maintenance records
Tail lights failing to illuminate (recurring)
Brake taillights fail to illuminate or illuminate improperly. Driver-side rear taillight is most commonly cited. Bulbs have been replaced but failure recurs every few weeks. Both taillights may fail simultaneously despite recent bulb replacement.
When: Around 60,000 miles in one case; recurring every 3 weeks
Symptoms owners cite: Driver-side rear taillight not illuminating while turning; Both brake taillights fail to operate simultaneously; Bulbs burn out repeatedly despite recent replacement; No warning lights on dashboard
Repairs/costs cited: Bulbs replaced by independent mechanic; failure recurring every 3 weeks
Recalls/TSBs owners mention: No dealer or manufacturer notification in narratives
Electrical fire hazard (melted fuses, overheating)
Interior lighting electrical circuit is drawing excessive current, causing repeated fuse melting. Emergency lights have stopped working due to overheating. A burned wiring harness was also documented in one narrative. Dealer unable to locate the root cause despite multiple visits.
When: Recurring multiple times over ownership period
Symptoms owners cite: Fuses melt repeatedly in interior lighting circuit; Burning smell detected in vehicle; Smoke exiting from hood; Wiring harness melted; Emergency lights non-functional due to overheating; Bulbs burn out due to overheating
Repairs/costs cited: Dealer unable to identify cause; one vehicle diagnosed with melted wiring harness but not repaired
Recalls/TSBs owners mention: NHTSA Campaign 21V749000 applies; manufacturer notified in some cases with delayed response
Synthesized from 24 NHTSA owner complaints — unverified consumer
allegations, summarized for patterns. The verbatim filings appear below.