A completely dead AC feels like a big repair — but a surprising share of "won't turn on" calls end at one of five cheap checks. Work them in order; each takes about a minute.
1. Thermostat first (seriously)
Set to COOL, setpoint 5°F below room temp, and if the display is blank or flickering, change the batteries. Dead thermostat batteries generate real service calls every single week of summer.
2. Both breakers
Your system usually has two: the air handler/furnace breaker and the condenser breaker. A tripped breaker sits in the middle position — flip it fully OFF, then ON. If it trips again immediately, stop and call a pro; repeated resets on a shorted circuit are how compressors and wiring die.
3. The float switch (the sneaky one)
If your indoor unit has a condensate safety switch and the drain backed up, the system is shut down on purpose. Look for a small switch on the drain pan or line; a full pan or wet switch means clear the drain and the "dead" AC resurrects.
4. The outdoor disconnect
The gray box on the wall next to the condenser has a pull-out block. Landscapers, kids, and previous techs leave these pulled or half-seated more often than anyone admits. Push it fully in (right-side up).
5. Hum but no start? That's the capacitor
If the indoor blower runs but the outdoor unit hums or clicks without starting, you've likely found the answer — the run capacitor is the most-replaced part in residential AC. Our free capacitor test confirms it in 60 seconds with a multimeter, and replacements ship same-day.
Still dead?
Run the guided compressor troubleshooter, or snap a photo of your unit's nameplate with our free AI decoder — knowing the exact model, age, and specs makes every next conversation (with a tech, with Mike in our chat, or with a parts search) ten times faster.
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