Not putting out heat
1. If the blower isn't working, could be motor itself, or a blown fuse/relay, dead resistor, faulty switch..... 2. If the blower works and you have no heat, check radiator coolant level. Really low coolant can prevent it from heating the core properly; a failed thermostat will act similarly. An air bubble in a heater line can block fluid passage..... 3. If these are OK, the ductwork has blend doors that move to get the temperature to the vent where you want it. Could be that the blend door that throttles between hot/cold is sticking because the door actuator is defective. You may have noticed a tapping sound under the dash from a defective actuator. Try a spray lubricant on the actuators, or remove them to see if there's a broken sprocket. Might need replacing. It's not a difficult fix.