Has your air conditioning stopped working?
If your AC unit has stopped working it is probably best if you go ahead and schedule an air conditioning service call with one of your local HVAC companies. Many times the company that you purchased your heating air unit from will come and take a look at your unit. Be sure to check with them to see if your heating and cooling unit is still under warranty. If your unit is still indeed under warranty it will not cost you anything to have it fixed.
Now, if your unit is no longer under warranty you to two choices to make. Choice number one being do you want to pay the company that you previously bought your HVAC unit from that is now broken. Or choice two being do you want to hire an entirely new HVAC contractor to install a new unit for you. This decision is completely up to you.