why did my air conditioner stop blowing cold air
When you turn on the unit, do you hear the compressor as well as the fan?
If you do not hear the compressor running, then it is possible that your AC unit either needs a reacharge or major repair. If the refridgerant pressure gets low, the compressor will either not start or may not cool sufficiently and you will only get warm air.
I would either call a professional or replace the ac unit (window type).