The first California heatwave hits and suddenly it feels like everyone’s AC stops working at the same time. One day your system is “fine.” The next day it’s 92°F inside, the thermostat is set to 72°F, the vents are blowing weak air (or none), and every HVAC company in town is booked out. Here’s the truth: HVAC systems don’t usually fail because the heatwave is “too hot.” They fail because the first real stretch of high demand exposes problems that were already building—dirty