AC won't turn on?

What usually causes this

These are the common possibilities, not a diagnosis. A page cannot tell which one it is — that takes a technician testing the system.

Thermostat

Dead batteries, the wrong mode, a schedule overriding your setting, or a blank screen can all stop the system from being called on at all.

Tripped breaker or disconnect

The indoor and outdoor units usually have separate breakers, and there is a disconnect switch next to the outdoor unit. A breaker that trips repeatedly points to an electrical fault.

Condensate float switch

Many systems have a switch that shuts everything off when the condensate drain backs up, to stop water damage. In a humid climate this is one of the most common reasons a system suddenly stops.

Failed capacitor or contactor

These start and switch the outdoor unit. When one fails, the outdoor unit may hum, click or do nothing.

Control board, wiring or a safety limit

A failed board, damaged low-voltage wiring (sometimes from pests or yard work), or a tripped safety control can keep the system off.

What you can safely check yourself

• Check the thermostat: screen on, set to Cool, set point a few degrees below room temperature. Replace batteries if it uses them.
• Check the breakers for the indoor and outdoor units. If one has tripped, reset it once. If it trips again, leave it off and call.
• Make sure the furnace or air handler door is fully closed — many have a safety switch that keeps the system off when the panel is loose.
• Look near the indoor unit for water in the drain pan or on the floor, which suggests the float switch has shut the system down.

What we check when we get there

1. 1A technician confirms power and the thermostat call, then works through the safety circuit — float switch, door switch, limits — to find what is holding the system off.
2. 2If the outdoor unit is the problem, the capacitor, contactor and compressor are tested rather than replaced on a guess.
3. 3If a blocked drain tripped the float switch, the drain is cleared and checked so it doesn't happen again next week.

What it is likely to cost

Many no-start problems are small repairs — a capacitor, a contactor, a cleared drain. A control board or compressor costs more. The diagnostic price is given before the visit, and the repair price before any work.

Diagnostic / service call

$89

Capacitor replacement

From $179

Contactor replacement

From $189

Condensate drain clearing

From $149

Control board

$449–$899

Basic thermostat replacement

From $199

Prices are starting points for standard work in the Savannah area. Final price depends on the system and site, and is confirmed before work begins. Permits and code-required upgrades may be additional.

Questions people ask about this

The thermostat is blank. Is the AC broken?

Not necessarily. Replace the thermostat batteries if it has them and check the breaker for the indoor unit. Some thermostats are powered by the system itself, so a tripped float switch or blown fuse can make the screen go blank too.

The outdoor unit hums but the fan doesn't spin. What does that mean?

Often a failed capacitor or a stuck fan motor. Switch the system off at the thermostat — running it this way can overheat the compressor — and schedule service.

Can a clogged drain really shut the whole AC off?

Yes. The float switch is designed to do exactly that so the drain pan doesn't overflow into the house. Drains clog more often in humid climates because the system removes so much water.

Where to go next