Some 2015-2019 Ford F-150 trucks equipped with a 3.3L, 3.5L Duratec, 3.5L EcoBoost and 5.0L engine and equipped with a block heater, and built on or before Jan. 1, 2019, may exhibit a lack of heat concern from the HVAC system when operating the vehicle in temperatures below 4 degrees Fahrenheit.
This may be due to deposits from the engine coolant becoming trapped in the heater core.
To correct, flush the cooling system and replace the heater core.
