No cold air when air conditioner is on?

Answer:
Most of the time, this is caused by:
a) a leak in your air conditioning system

which leads to

b) depletion of your freon (the cooling liquid that your A/C uses).

Get a A/C service from your mechanic and ask them to check and repair any leaks.
First answer by Homerless. Last edit by Homerless. Contributor trust: 1 [recommend contributor recommended]. Question popularity: 2 [recommend question].