Why does a heater blow and not get warm?

Your problem is that your heater core is plugged up. If you do a back flush on the system, this should fix your problem. If it does not, you will need to replace your heater core. They(heater cores) do not always show leakage in the vehicle. Sometimes it will leak on the engine and evaporate(fluid). The heater core on your vehicle is being by-passed. Lol have someone check the heater coil - it's most likely bad Could be a lack of coolant circulation. Is your cooling system full? In reference to one of the previous answers, you would know if your heater core was bad because you'd have massive amounts of coolant leaking from your dash into the interior of your car. Check to see if your heater hoses are hot or not. You might have a coolant circution problem, in which case i would check the thermostat. In my jeep, the air wasn't warm, and I had a blend air door problem beneath the dash. Plugged heater CORE, check as mentioned above, low coolant, air pocket, themostat stuck. Poor circulation as mentioned.