Nothing happens when the thermostat calls for cooling — no indoor fan, no outdoor hum, just silence. A completely dead system is alarming, but the cause is often simpler than it feels.
Work through the safe checks below in order. They resolve a surprising number of dead-system calls without a visit.
Check These First
Thermostat: fresh batteries if it takes them, set to cool, setpoint below room temp. Then the breakers — there are usually two: one for the indoor air handler and one for the outdoor condenser. If either tripped, reset it once. If it trips again immediately, leave it off and call.
Condensate float switch: find the indoor unit and look for a small device on the drain line with the system wired through it. If the drain pan filled with water — algae clogs are the classic Stuart cause — the switch kills the system to prevent a flood. Clearing the drain or calling us to clear it brings it back.
What It Is When the Simple Stuff Checks Out
A failed capacitor or contactor — power reaches the unit but nothing starts. A failed control board or transformer — the low-voltage signal never leaves the thermostat. A seized blower or compressor motor. Or storm damage: Martin County lightning loves control boards, and a surge can kill a system silently overnight.
All of these are confirmed with meters in a few minutes on a diagnostic visit. None of them are homeowner repairs — capacitors store a charge that can hurt you with the power off.
After a Storm
If the AC died during or right after a thunderstorm, suspect the electrical side first: tripped breaker, tripped float switch from a power blip, or a surge-damaged control board. Check the breakers once, then call — and ask us about whole-home surge protection while we're there, because the next storm is already scheduled.
Common questions
The thermostat is blank. Is that the AC or the thermostat?
Could be either — dead batteries, or the float switch cut power because the drain backed up, or a failed transformer. Check batteries first, then look at the drain area for standing water.
I reset the breaker and it tripped again instantly. Now what?
Leave it off and call us. A breaker that won't hold is protecting you from a short or a seized motor — forcing it risks damage.
Can a clogged drain really shut down the whole system?
Yes — that's exactly what the float switch is for. Algae-clogged drains are one of our most common no-cooling causes, and clearing the line usually brings the system right back.
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