Heater blowing cold air on 2007 Dodge Magnum

I had to put some stop leak in the radiator and suddenly the heater starting blowing only cold air. What might it be?

Asked by for the 2007 Dodge Magnum
1 answer
You may have plugged up the heater core, which is why some people recommend against using this stuff. Try flushing the heater core and see if it is plugged.