Check These 3 Things Before Using Your Air Conditioner from foxnews.com
1. Change filters regularly (every 30 to 60 days depending on filter type).
2. Clean the vents indoors and on the outdoor unit itself — don't make the air conditioner work more than it has to.
3. Remove any sludge or grime from the drainage pipe. A wet-dry shop-vac can go a long way towards making sure things flow smoothly — just attach to the end of the drain pipe and suck out any grime that may be accumulating.