Hyundai Sonata overheating problems

Filed Oct 3, 2026 · Electrical · GA

The passenger compartment climate control blower motor circuit suffered a severe thermal overload. The terminal overheated, shorted out, and physically melted the primary engine wiring harness (Part #91400-L0051) inside the main fuse block connector housing while the vehicle was operating. This caused an immediate smoke/fire hazard in the cabin and a total loss of window defogging and climate control functionality. This structural breakdown is directly tied to the electrical failures documented in Hyundai TSB #WTY037 / 25-EE-002H.

Filed Sep 7, 2026 · Electrical · AR

A/C blower motor fan would stop working. Happened twice within less than a year apart. Upon further inspection, multi fuse wiring overheated and melted, ruining fuse and making A/C stop working during 100+ temperatures outside. Apparently this is a well known issue with this make and model Sonata. Electrical failure.

Filed Sep 3, 2026 · Electrical, Transmission · TX

I am submitting a safety complaint regarding a recurring, unresolved electrical defect in my 2020 Hyundai Sonata SEL. The vehicle fails to recognize when the ignition is switched off, leaving core vehicle systems active and causing severe parasitic battery drain that leaves the car immobilized. ​Description of the Problem: ​False "On" Status: After parking, turning off the engine, and exiting the vehicle, the car continues to register as though the ignition is still active/on (accessories, cluster, or vehicle network remain awake). ​ Severe Parasitic Draw: Because the vehicle fails to shut down its electrical circuits, the 12-volt battery repeatedly discharges overnight or while parked for short durations. ​Battery Replacement Did Not Resolve Issue: The 12-volt battery was replaced with a brand-new unit to eliminate typical wear, yet the drain and false "on" behavior persisted immediately. ​ Frequency: The vehicle frequently fails to start, requiring constant jump-starts or roadside assistance to operate. ​Safety Hazard: This defect creates a direct safety risk by repeatedly stranding the driver without warning in public locations, traffic stops, or remote areas. In addition, an electrical system that fails to enter a sleep state creates a potential hazard for component overheating, failure of electronic security and locking systems, or total electrical failure while attempting to restart or operate auxiliary safety equipment. Other Hyundai owners have reported identical issues where the body control modules or ignition logic fail to power down. ​Corrective Action Requested: I request that the federal safety agency investigate this electrical shutdown defect across the 2020 Hyundai Sonata model year to identify whether a faulty Body Control Module (BCM), smart key receiver, or ignition switch relay requires a safety recall and software or hardware remediation. Battery replaced on 09/04/2026 Car inspected/diagnosed by Hyundai Dealership on 09/03/2026

Filed Aug 18, 2026 · Engine · 140,000 miles · FL

The contact owns a 2019 Hyundai Sonata. The contact stated that while driving at an undisclosed speed, the vehicle experienced severe overheating and excessive oil consumption. The contact also stated that there was a misfire in the engine even though the spark plugs and ignition coils were replaced. Due to the failure, the vehicle could not be driven with the air conditioning activated. Additionally, the engine was knocking and shaking abnormally, causing an oil leak and a smoke odor due to the oil burning. The vehicle was taken to a dealer, where an engine replacement was recommended. The vehicle was not repaired. The manufacturer was notified of the failure. The failure mileage was 140,000.

Filed Aug 18, 2026 · Electrical · NJ

The AC/heating blower motor circuit on my 2020 Hyundai Sonata failed intermittently due to extreme electrical resistance overheating and melting the terminal pins inside the engine fuse box. I took it to the dealership and they inspected it said it was out of warranty but it needed part number 18980-09910-FFF and wiring kit 91300L1000-FF to repair at a cost of 780.00 including parts, tax, and labor. This matches the severe design defect acknowledged in Hyundai TSB #25-EE-002H or alternative TSB-24-EEOO-1H. I filed case number 43138757 with Hyundai corporate. For now this just affects my air conditioning. However, the root failure is a known design defect that presents a severe vehicle fire hazard and potential loss of windshield defrosting capability, lights, etc. if the whole electrical system should fail. As you should know the engine bay fuse box (which currently has melted parts) is the "brain" for the car's electrical distribution. It doesn't just power my AC fan; it holds the fuses and relays for the cars fuel pump, engine control module (ECM), headlights, and electronic power steering. If left unfixed and over time as the plastic melts, copper wires will cross and touch each other, causing a massive short circuit. My engine could suddenly cut out and stall while I am traveling at 70 mph on the highway, instantly killing my power steering and power brakes and putting me in extreme danger. Again not to mention the fire hazard this situation is likely to cause. This should be addressed via a mandatory safety recall, so that I don’t have to pay for a known engineering design defect and in case the TBS bulletin fails or further unknown damage has already occurred.

Filed Aug 13, 2026 · Engine · NJ

On January 26, 2026, my 2019 Hyundai Sonata SEL suddenly became inoperable overnight. The vehicle had been operating normally with no warning signs—no check-engine or oil-pressure light, abnormal engine noise, overheating, loss of power, or other indication of an impending failure. The following morning, the engine would not start. The vehicle was towed to an independent mechanic on January 28, 2026, who determined that the engine was locked/seized. On February 11, 2026, it was towed to Wayne Hyundai for further diagnosis. The vehicle had only 51,533 miles and had received Hyundai’s Knock Sensor Detection System (KSDS) update. Hyundai denied warranty coverage, citing engine sludge, despite my providing a complete service history after resubmiting the missing receipts I had previously misplaced. My primary concern is safety, not the warranty dispute. A sudden engine seizure without warning could cause an unexpected loss of propulsion or create a dangerous situation if the engine fails while the vehicle is being driven. This concerns me because Hyundai Theta II engines have previously been associated with engine seizure and stalling, including issues addressed through The Hyundai Theta II Engine Settlement: and subsequent litigation involving certain 2019 Sonata vehicles. I respectfully request that the federal safety agency investigate whether a continuing or insufficiently addressed engine defect exists in affected 2019 Hyundai Sonata vehicles, particularly sudden engine seizure/no-start failures occurring without warning. I also ask the federal safety agency to examine whether existing recalls, campaigns, software updates, warranty extensions, and other remedies adequately protect owners when an engine fails suddenly before the KSDS system provides a warning.

Filed Aug 5, 2026 · Engine · CA

Engine / Short block assembly / Connecting rod bearing seizure. The engine suffered a sudden, catastrophic seizure while I was actively driving on a steep incline mountain road with a cliff on one side and forest on other. The vehicle experienced an immediate, total loss of motive power, forcing an emergency maneuver onto the shoulder in 5 seconds with no power steering or power brakes, creating an extreme collision hazard on a high-speed incline. The rod bearing melted due to a manufacture defect and could have also possible caught fire in heavy fire country. The fuel pump was also leaking recently and just replaced. They are nearly $1800 for a new pump because of price gauging because they are in "high demand". The Check Engine Light was solid (not flashing) for a thermostat code (P0128) due to extreme internal friction/heat from the failing bearings. There were no flashing KSDS warnings or physical signs of engine overheating. My car was denied a new engine under a Federally Mandated Warranty explicitly stating the exact symptoms of internal engine defect that happened in my car under "owner neglect" even though I have changed my oil regularly and even before the manufacture recommended time frames to do so. I've changed the valve covers, 02 sensors, thermostats, and plenty more on this car than any other car I have ever owned proving I'm actually an exceptional owner. I remained nice to all corporate staff during this process while they denied my car proper care under a Federal Mandate. I bought this car to believe that Hyundai was a superior company in regards to warranties, price, and function as opposed to the more expensive counterparts of the same class. Which in the end has cost me way more, and almost my life. This car is dangerous and the company has done everything in their power to try to cover it up while placing blame on the very consumers that are believing in them to do better.

Filed Jul 13, 2026 · Engine · MO

The check engine lights blinking, it overheats and it shuts down.

Filed Jul 9, 2026 · Engine · 74,000 miles · VA

The contact owns a 2015 Hyundai Sonata. The contact stated that the vehicle was taken to a local dealer who performed an emission software upgrade. Later, while driving, the air conditioner blew hot air, the thermostat increased to high, and an engine overheating warning message was displayed on the instrument panel. The vehicle was taken back to the dealer, who diagnosed that the thermostat had failed and needed to be replaced. The thermostat was replaced, and the failure was remedied. The manufacturer was notified of the failure. The failure mileage was 74,000.

Filed Jun 24, 2026 · Engine, Fuel system · SC

At approximately 130,000 miles, vehicle developed and internal coolant leak caused by a failed Exhaust Heat Recovery System (EHRS) in the center muffler assembly, matching TSB 23-EM-009H - a known manufacturing defect documented by Hyundai. Coolant has been slowly leaking internally into the exhaust system. The authorized Hyundai dealership initially failed to diagnose the internal leak and told me there was no leak and wanted to send me home. After pushing back, the internal leak was confirmed. If not caught, this defect could result in engine overheating or complete engine failure without warning. Hyundai Motor America has denied goodwill coverage despite this being a documented manufacturing defect.