No Heater After draining cooling sytem

Help!
I drained my radiator and filled it with new coolant. Now I noticed that my heater only blows cold air.

Yep, it will do that when you get air stuck in your cooling system.
Air doesn't transfer heat very well and that is why the heater is not working.

The cooling system is normally filled entirely with a water/antifreeze mix.
When the coolant was drained air went in which is normal. But when you put new fluid in air can get trapped at various points of the cooling system.

You need to purge the air from the cooling system by venting it at one of the highest points in the cooling loop (since air naturally rises).
Some vehicles have a vent or valve for doing that. If your's doesn't you can loosen a cooling line at a high point and let the air out as you add more coolant.

This must be taken care of before using the vehicle because air doesn't provide proper cooling for the engine. You have already observed this since the heat from the engine isn't making it to the heater.

If you can't vent the air you could run the engine a short time (2-5 minutes) just enough to open the thermostat and then try again. You'll know when you get it because the antifreeze level will go down and then you can finish filling it up.

take off radiator cap start car let air come out. after thermostat opens.

on the left side of the radiator there is a bleeder for it open it with a screwdriver in fill the radiator full until coolant starts to come out of it.with coolant. it may also be a heater core gone bad.