The contact owns a 2021 Chevrolet Trailblazer. The contact stated that while the vehicle was parked, the vehicle was turned off however, the blower fan independently activated. No warning light was illuminated. The contact’s husband had just parked the vehicle upon arriving at the place of employment. The contact’s husband is a certified mechanic. The vehicle was diagnosed with coolant intrusion and a misfire in the engine. The contact was informed that the spark plugs needed to be replaced; however, the spark plugs had to be ordered. The vehicle was not repaired. The vehicle was driven to the residence. The contact’s husband parked the vehicle and turned the vehicle off. The vehicle failed to start as intended and was towed to the dealer to be diagnosed and the dealer determined that there was a crack in the head gasket. The contact was informed that the head gasket needed to be replaced. The vehicle was not repaired. The manufacturer was made aware of the failure. The contact was advised to contact the NHTSA Hotline to report the failure and a case was filed. The failure mileage was approximately 128,000.