Guide
Your AC is running but the house is not cooling: check these first
Five things a Miami homeowner can check in ten minutes, and the three that mean stop and call.
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Updated October 2026
When a Miami AC runs but won't cool, check five things first: the thermostat setting and batteries, the air filter, the breaker, water in the air handler's drain pan, and whether the outdoor unit's fan is spinning. If you see ice on the lines, a repeatedly tripping breaker or a burning smell, switch the system off and call rather than keep checking.
By Nelson Galloway, Cooling and Refrigeration Guides Editor · Updated October 2026
Check 1: the thermostat
It sounds obvious, but it's the first thing a technician checks. Make sure the thermostat is set to cool, the setpoint is below the room temperature and the fan is on auto. Replace the batteries if it has them. A blank screen can mean dead batteries, or that something has cut power to the whole system, which leads to the next checks.
Check 2: the air filter
A clogged filter starves the system of air, and in a system that runs as much as a Miami AC does, a filter can load up in a month or two. Pull it out and hold it to the light. If you can't see through it, replace it. A badly clogged filter can also freeze the coil, so if the filter was bad, switch cooling off and run the fan for a while before trying again.
Check 3: the breaker
Look at the panel for the AC breakers, usually one for the air handler and one for the outdoor unit. If one has tripped, reset it once. If it trips again, leave it off. A breaker that keeps tripping is protecting something, often a failing motor or compressor, and resetting it repeatedly can turn a repair into a replacement.
Check 4: water in the drain pan
Open the air handler closet and look at the pan under the coil and around the base. Water there usually means the condensate drain is clogged, and many systems have a float switch that shuts the AC off when the pan fills. That looks like a dead system, but it's a drain problem. Mop up, and if you have a cleanout on the drain line, a wet-vac on the outdoor end of the line sometimes clears it.
Check 5: the outdoor unit
With the system calling for cooling, go outside and look at the condenser. The fan on top should be spinning and you should hear the compressor running. If the unit is humming but the fan isn't turning, switch it off; a stalled fan motor or a failed capacitor overheats the compressor quickly. Clear any leaves, grass or debris packed against the coil.
What a technician checks next
If your checks don't find it, a technician works through the parts you can't safely test: the capacitor and contactor in the outdoor unit, the amp draw of the compressor and fan motors, the refrigerant charge measured with gauges, the temperature drop across the indoor coil, and the condition of the coil and blower wheel. Most no-cool calls come down to one of those, and the diagnosis should come with the reading or the failed part shown to you before any repair is priced.
When to stop checking and call
Some signs mean switch the system off and call right away: ice on the copper lines or the indoor coil, a breaker that trips again after one reset, a burning or electrical smell, a loud grinding or clanking from the outdoor unit, or water coming through a ceiling. Refrigerant work, capacitors and electrical testing all need a technician with the right meters.
If you need a technician
Related services
AC Repair
AC blowing warm air, AC tripping the breaker.
Emergency AC Repair
24 hour AC repair, AC stopped cooling overnight.
Frozen AC Coil Repair
Ice on the refrigerant line, AC freezing up at night.
AC Drain Line Cleaning
Clogged condensate drain, float switch shutting the AC off.
FAQ
Questions about this guide
Common causes are a clogged filter, a frozen coil, a failed capacitor or fan motor, low refrigerant or a tripped float switch.
If there's ice, a tripping breaker or a burning smell, yes. Otherwise try the five checks, then call.
No. Low refrigerant means a leak, and retail cans can damage the system and hide the problem.
If the checks don't fix it within half an hour, call. In Miami heat, a house warms up quickly.
Want a technician to look at it?
Call the Miami office any hour and a person answers.
