Depending on the age of your a/c you may want to have it serviced or replaced. That's only one solution. If there is demand for your unit you may want to consider it. Just remember to keep loyal renters in mind and offer them this years rates if they book now, this is common practice in the rental community. Keep in mind if you raise your rates too high you may scare away prospective renters and either lose money or just break even.
If you use a rental company make sure you discuss it with them as well. They may advise against it or advise you to only raise them slightly. Oh and since I'm rambling, you don't have to raise across the board, some people only raise certain peak times. ;-)