AC not cooling in Miami: what to check before you call, and what not to touch

The system is running, or it is not, and either way the house is getting hot. Before the call, these checks take a couple of minutes and, on a good day, end the problem. On a bad day they tell the contractor exactly what to bring.

Check first

The breaker. Open the panel and find the AC breakers. Most Miami homes have two: one for the air handler inside and one for the condenser outside, often a double breaker labeled AC or A/C. If one is tripped (in the middle position or off), reset it once. If it trips again within minutes, stop. Something is drawing too much current, and resetting it repeatedly can turn a small repair into a burnt compressor.

The thermostat. Set to Cool, fan on Auto, temperature at least three degrees below the room. If the screen is blank and the thermostat takes batteries, replace them. If it does not take batteries and the screen is blank, the system’s low-voltage transformer or the float switch has cut power to it, and that is a contractor visit.

The filter. A filter clogged solid strangles airflow, which freezes the indoor coil, which shuts the system down or makes it blow warm. Pull it out; if you cannot see light through it, replace it. Then give the system an hour off before trying again.

Water at the air handler. Look at the floor around the indoor unit and inside the closet. Standing water means the condensate drain is clogged and the float switch has done its job and cut the system off. This is the most common shutdown in Miami. Do not bypass the switch; the water it is protecting you from goes into the ceiling below or the floor.

The outdoor unit. Go outside. Is the fan on top spinning? Is the unit humming or clicking? Is it buried in leaves, or has a hedge grown against it? A fan that is still while the unit hums is usually a capacitor, the cheapest common repair there is. A unit choked by plants needs two feet of clearance to breathe.

Stop and call

• Ice on the copper lines or the coil. Turn the system off at the thermostat (you can leave the fan On to speed the thaw). A frozen system cannot be diagnosed until it thaws, and running the compressor against a frozen coil can destroy it. This is the expensive mistake.
• Burning smell, buzzing, or a breaker that keeps tripping. Leave the breaker off. Electrical.
• The system starts, runs a minute, and stops, over and over. Short-cycling. It can be a float switch, a pressure switch, a bad thermostat, or an oversized system, and it needs to be seen running.

What not to touch

Do not open the outdoor unit; the capacitor inside holds a charge even with the power off. Do not buy a recharge can. Refrigerant is handled by EPA-certified technicians for a reason, the can does not tell you why the system is low, and “topping off” a leaking system is not a repair. Do not pour bleach into the drain line unless you know it does not run through the air handler’s evaporator pan; a contractor uses the right treatment and clears the line properly.

While you wait

Blinds closed on the sun side, ceiling fans on, doors closed, no oven. If someone in the house is elderly, very young, pregnant, or unwell, do not ride out an 88 °F house waiting for a visit; go somewhere cool. When the contractor calls back, tell them what you found: which breaker, whether there was ice or water, what the outdoor unit was doing. It changes what they bring.

Call and say what the system is doing.

Related pages

• AC not cooling: call now
• AC repair in Miami-Dade
• AC maintenance