Cranking up strong and reliable air conditioning systems is the best way to beat the summer heat, especially if you don’t have a pool or lake nearby where you can take a quick dip. As a result, it should come as no surprise that, in 2012, an estimated 87% of American homes used some form of AC. But, unfortunately, even the most dependable units do not last forever, even if homeowners invest in the necessary air conditioning services and upkeep. In the same way that your beloved old car isn’t going to run forever, at some point you’ll need an AC replacement. Thankfully, there are a handful of signs that let you know when it’s time.