Why does the heater not get hot

Check the coolant level,it must be full to get proper heat,if not full the coolant won't circulate through the heater core to produce proper heat. both heater hoses from heater core should be VERY HOT to try and hold with your hands when engine is at normal operating temperature! Where is the temperature hand at after engine is at normal operating temperature? It should be about halfway between C and H on the gauge,if it's just barely moving from C,suspect failed thermostat.