AC Won't Turn On — Working Through It

Nothing happens at all — no fan, no outdoor unit, no click. Several of the causes cost nothing to rule out.

Worth attention today

In Florida summer this becomes urgent quickly, particularly with children, elderly residents or pets in the house. We answer 24 hours a day for exactly this.

(561) 814-1600 AC Repair

A completely dead system is frustrating but it is also one of the more tractable symptoms, because a decent share of the causes cost nothing to rule out and you can do it in five minutes. Work through the free checks first — not because we do not want the call, but because arriving to flip a breaker back on is a bad outcome for everybody.

The most common Florida cause of an apparently dead air conditioner is not electrical at all. It is the condensate safety float doing its job: the drain line blocks, the pan fills, the float opens the control circuit and the system shuts down. There is no error message and nothing looks wrong. It presents as an intermittent electrical fault — off for a while, working later — and it is very often the answer.

Describe what it's doing

Tell us the symptom and we'll tell you what it usually is.

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Prefer to talk? (561) 814-1600 — 24/7.

Before you call anyone

Check these first — they cost nothing

Thermostat: on COOL, set below room temperature, and the display is actually lit
Thermostat batteries, if it takes them — a surprising share of dead-system calls end here
The breakers for BOTH the air handler and the outdoor unit; there are usually two
The outdoor disconnect box beside the condenser has not been pulled out
The service switch by the indoor unit — it looks like a light switch and gets flipped by mistake
The condensate pan: if it is full of water, a float switch has shut the system down
The filter is not so clogged that the system has iced up and tripped a safety

Testing the electrical components inside an air conditioning service panel

If the checks above do not resolve it, the causes below need instruments — pressures, temperature split and static pressure — rather than guesswork.

What it usually turns out to be

A tripped condensate float switch

The most common Florida cause. The drain is blocked and the safety has done exactly what it exists to do. Clearing the drain is the fix; the electrics are fine.

A blown low-voltage fuse or failed transformer

The 24-volt control circuit is dead, so nothing is commanded to run even though line power is present. Usually a small part, sometimes a short in the low-voltage wiring behind it.

A failed contactor

The outdoor unit is never switched on. Everything else may behave normally, which is why the outdoor unit is worth checking specifically.

A dead or miswired thermostat

Particularly after a smart thermostat has been installed. Common-wire problems produce exactly this and are easy to miss.

A tripped breaker that will not reset

A breaker that trips again immediately is reporting a fault, not causing one. Repeated resetting is genuinely unsafe — stop and call.

A failed control board

Less common, but it is the answer when everything upstream tests good and nothing downstream is being commanded.

AC Repair (561) 814-1600

AC Not Turning On — common questions

How many breakers should I be looking for?

Usually two — one for the indoor air handler, often a smaller one, and a larger double-pole breaker for the outdoor condenser. People check one, find it on, and stop. Check both.

It came back on by itself after a few hours.

That is the signature of a condensate float switch. The pan drains slowly, the float drops, the system restarts. It will keep happening, and each time the pan is full there is water sitting above your ceiling.

Is it safe to keep resetting the breaker?

Once, to see whether it holds. If it trips again, no. A breaker that trips repeatedly is protecting the circuit from a genuine fault, and forcing it is how electrical faults turn into fires.

Want someone to just look at it?

Open 24 hours, 7 days a week. Someone answers the phone at 3 AM. Not a machine.

(561) 814-1600