Some 2015-2017 F-150 vehicles equipped with a 3.5L Duratec or 5.0L engine may exhibit a lack of heat concern from the heating ventilation and air conditioning (HVAC) system when the vehicle is operated in temperatures that are consistently below -20 Ã…?C (4 Ã…?F). This condition may be due to deposits from the engine coolant becoming trapped in the heater core. Follow the Service Procedure steps to correct the condition.