It's not so much the cranking down of the thermostat (you can get ones that have preset limits to prevent abuse) as leaving the doors and windows open. Here's the check list I used when a renter called about a malfunctioning air conditioner:
1. How long ago did you check in, the housekeepers generally set the thermostat to 78 degrees and to cool down will take some time.
2. Are the doors and windows open, the a/c will not cool the neighborhood.
3. Is there any air flow when hold your hand in front of a vent when the a/c is on?
If yes, then you may have to wait no air conditioner will cool an entire condo, house, or any other structure in 10 minutes. Especially when you are unloading a car of it's contents and opening and closing the door.
If no, then you have successfully frozen up the coil. This happens when the unit operates with heavy humidity this only happens when doors and windows are open. Eventually the layer of ice that forms on the coiling coils builds to a solid block of ice. Turn the a/c unit completely off and wait 4-6 hours for it to melt. Never explain to a renter that they can use a hair dryer or turn the unit to heat to speed up the process.
Mills heating and air conditioning offers a spring maintenance check up every year and it's worth every penny. Basically they'll look over the unit and tell you if it needs additional freon, replacement parts, or full replacement. In addition I recommend them since they offer a 10 year additional warranty that covers parts and labor. Considering that the exterior unit of a condo or house a/c system will not last 10 years in our salt air it's basically a free replacement in 4-6 years. It's also invaluable when it breaks on July 4th as you pay nothing for the repairs.
