AC Not Cooling After a Power Outage? Do This First

First: wait five minutes before deciding anything is broken

Most modern systems have a built-in delay of roughly three to five minutes before the compressor is allowed to restart. It exists to stop the compressor starting against high head pressure, which is genuinely damaging. So a system that sits silent right after power returns is often behaving exactly as designed.

Set the thermostat where you want it, then leave it alone for five minutes. A surprising share of post-outage calls resolve themselves in that window.

Then check, in this order

• Thermostat. Screen lit? Set to COOL, fan on AUTO, setpoint below room temperature? Some thermostats lose their programming after an outage and come back on a default schedule.
• Both breakers. There are usually two — indoor air handler and outdoor condenser. A tripped breaker does not always look obviously off; flip it fully OFF, then back ON.
• The outdoor disconnect. The pull-out box on the wall beside the condenser. Confirm it is seated.
• The float switch. If the system ran with restricted drainage during the outage, or condensate backed up, a float switch may have cut power. Look for standing water in the drain pan.

The mistake that turns a reset into a repair

If the breaker trips again immediately, stop. Do not keep resetting it. A breaker tripping repeatedly is protecting you from a real fault, and each reset sends another surge through a compressor or a motor that may already be damaged.

The same applies to a unit that hums but will not start, or one that starts and stops within seconds. Switch it off at the breaker and leave it off until someone can look at it. Continuing to cycle it is how a capacitor failure becomes a compressor failure.

Why outages damage air conditioners here

The damage is rarely from the outage itself. It is from the restoration. Power coming back after a South Florida storm or a grid fault often arrives unstable — sags, brief surges, sometimes several cycles in a row as the utility brings circuits back. A compressor asked to start into a voltage sag draws far more current than normal, and that is what kills capacitors and, eventually, compressors.

This is exactly why the standard advice before a known outage is to switch the system off at the thermostat and the breaker, then bring it back up manually once power has been steady for a while.

What a technician will look at

The usual post-outage findings, roughly in order: a failed run capacitor (common, inexpensive, and the reason a unit hums without starting), a tripped internal overload on the compressor, a blown low-voltage fuse on the control board, a contactor with welded or pitted points, and least often, a damaged compressor.

A surge protector at the outdoor unit is cheap insurance in this climate and worth asking about while someone is already there.

When to treat it as urgent

Rising indoor temperatures with an elderly resident, a young child, or anyone medically vulnerable in the house is not something to wait out. Say so when you call — overheating homes get triaged ahead of routine appointments.