Why Your AC Stops Working in the Middle of a Texas Summer

The First Thing to Understand About Texas Heat

A house in the Magnolia or Tomball area loses its cool air surprisingly fast when the AC stops. In July or August, a well-sealed home can climb two degrees per hour once the system is down, and once interior temperatures cross 85 degrees, the unit has to work significantly harder to pull the space back down. That means the sooner you identify and fix the problem, the less strain your equipment takes getting the house comfortable again.

Most summer AC failures come from a short list of causes. Before calling for service, it is worth spending five minutes on the ones you can check yourself.

Check These Four Things First

• Thermostat settings. Confirm the thermostat is set to cool, with the fan on auto, and the target temperature below the current room temperature. A thermostat accidentally bumped to heat or fan-only mode accounts for more service calls than you would expect.
• The breaker panel. Find the breaker for your air handler and the one for your outdoor condenser. If either has tripped to the middle position, reset it once. If it trips again immediately, leave it off and call. A breaker that will not hold is warning you about something downstream.
• The air filter. A filter packed solid with dust restricts airflow until the evaporator coil freezes solid. A frozen coil shuts the system down. Pull the filter out and look at it. If you cannot see light through it, replace it and wait 30 minutes with just the fan running before trying to cool again.
• The outdoor unit. Walk outside and listen. If you can hear the condenser humming but the fan is not spinning, the run capacitor has likely failed. If there is no sound at all and the breaker is on, the contactor or control board may be the issue. Do not attempt to reach inside the unit yourself.

The Most Common Parts That Fail in Summer

Run capacitors are the single most common summer failure in this region. Every AC condenser has at least one, and electrolytic capacitors degrade faster in sustained heat and humidity. A technician can test capacitor value with a meter and spot a weak one before it fails completely. That is one reason annual maintenance in spring catches so many problems before they strand you.

Contactors are the second most common. The contactor is a relay inside the condenser that switches power to the compressor and fan motor. The contact faces pit and burn over thousands of switching cycles, and they eventually fail to close. A technician can see the condition of the contacts in a few seconds.

Condensate drain clogs are the third. In the humidity levels that Magnolia, Pinehurst, and Conroe see from May through September, the condensate line is draining a significant amount of water every day. Algae and debris build up in the PVC line, eventually clogging it. When the drain backs up, a safety float switch shuts the system off before water can overflow into your ceiling. Flushing the drain line with diluted bleach once a season prevents most clogs.

When Refrigerant Is the Problem

An air conditioner does not consume refrigerant the way a car burns gasoline. If your system is low on refrigerant, it has a leak somewhere. Refrigerant leaks commonly occur at the service valves, at coil joints that have vibrated loose over years, or at hairline cracks in the copper tubing. A leak repair involves finding the breach, fixing it, pulling the system into a vacuum to remove moisture, and recharging by weight. It is a several-hour job done correctly.

If your system was manufactured before 2010 it may run on R-22, which is no longer produced in the United States. Available stock is limited and the price reflects it. A technician who finds a significant R-22 leak will give you an honest comparison between repair-and-recharge and replacing the equipment with a modern R-410A or R-454B system. Neither is a trivial expense, and the right answer depends on the age and overall condition of your equipment.

Spring Maintenance Prevents Most of This

The failures described above are mostly detectable before they strand you. Annual maintenance in March or April, before the first heat of summer, catches weak capacitors with a meter reading, checks the contactor face, flushes the condensate drain, verifies refrigerant charge, and cleans the outdoor coil of cottonwood and debris. None of that is visible without opening the unit, which is why the system can feel fine on a 70-degree April day and then fail on the first 95-degree day in June.