Heater doesn’t work changed out resistor and thermostat. Blower Motor works fine what else could it be?

Hi, the resistor is only a concern if the fan only blows at high speed. It has nothing to do with the air being hot or cold. The thermostat does regulate engine temperature - but did you purge the air out of the cooling system when you replaced it? Have you verified engine temperature is proper - the thermostat opens between 176-190 degrees, depending on the engine, and runs at about 212 or more degrees with the thermostat fully open (Fahrenheit). With the coolant this hot, you should have heat inside the car, as long as the climate control system is functioning properly inside the vehicle. A series of doors and motors directs air flow and temperature; there could be a concern there. www.repairpal.com/repair-shops