Don't forget that your furnace filter still needs to be changed regularly, even in the summer! If your air conditioner is running but the air flow is impeded by a dirty filter, it can cause the coil to freeze up. Ice buildup on the coil can cause damage and refrigerant leaks.
The first sign of this is that your a/c will not keep up to the temperature you have set. Turn it off, check the filters. If dirty, remove and replace with clean. If unsure, just remove it to test. Allow the coil to completely thaw, then startup the a/c again with either a clean filter or no filter. If it keeps up to the set temperature without freezing up, that was the problem! If it still does not keep up to temperature set, give us a call and we can perform a complete system check.