John Carlsen has more than a decade of experience testing and reviewing home tech products, with a major focus on smart home security. He earned his BS in journalism from Utah Valley University. In ...

It's always in the middle of a heatwave. Your AC hums to life, but instead of the icy rush you're craving, it pushes out a faint, lukewarm breeze. That's when the dread sets in. Is the unit failing?