AC Not Cooling? What to Check Before Calling a Tech in Austin

Your AC stopped cooling. The house is getting warmer by the minute, it is 102 degrees outside, and you are trying to figure out whether this is a simple fix or a call to an HVAC tech. We get it. This is one of the most stressful situations for Austin homeowners, and we take dozens of these calls every week from May through September.

Before you schedule a service call, there are several things you can check yourself that might solve the problem — or at least help you describe the issue accurately when you do call. And knowing the difference between a quick fix and a serious problem can save you time, discomfort, and money.

Check Your Thermostat First

This sounds too simple to be the answer, but we show up to thermostat-related calls more often than you would expect. Here is what to verify:

• Make sure the thermostat is set to COOL, not HEAT or AUTO HEAT. Someone bumped it, a kid played with it, or a firmware update reset the settings. It happens.
• Check that the fan is set to AUTO, not ON. When the fan is set to ON, it runs continuously even when the compressor is not actively cooling. The air coming from your vents will feel warm or lukewarm because the fan is just circulating unconditioned air.
• Verify the set temperature is below the current room temperature. If the thermostat reads 76 and is set to 76, the system has hit its target and will not run.
• If you have a smart thermostat (Nest, Ecobee, Honeywell Home), check whether it has gone into a recovery mode, eco mode, or energy-saving schedule that raised the temperature automatically. Smart thermostats sometimes make decisions you did not ask for.
• Check the thermostat batteries if it is battery-powered. A dead thermostat means no signal to your system. Many thermostats flash a low-battery indicator, but not all of them.

If the thermostat looks correct and the system still is not cooling, move on to the next check.

Replace Your Air Filter Right Now

If you have not replaced your air filter recently, go do it before you read the rest of this article. In an Austin summer, air filters should be replaced every 30 days — not every 90 days like the packaging suggests. Austin's cedar pollen, oak pollen, dust, pet dander, and general particulate load clog filters faster than most cities in the country.

A clogged air filter restricts airflow across the evaporator coil inside your air handler. When airflow drops below what the system needs, the coil gets too cold and freezes over. A frozen evaporator coil cannot absorb heat from your home, so the air coming from your vents feels lukewarm or barely cool even though the system is running.

Here is how to check:

• Locate your return air filter. In most Austin homes, it is either in a hallway ceiling grille, a wall grille near the air handler, or at the base of the air handler unit in the attic or closet.
• Pull the filter out and hold it up to the light. If you cannot see light through it, it is too dirty.
• Replace it with the correct size. The size is printed on the frame of the old filter. Keep a few spares in the closet so you are never caught without one.

After replacing a clogged filter, give the system 30-60 minutes to recover. If the coil was frozen, it needs time to thaw before the system can cool effectively again. Turn the system to FAN ONLY mode for an hour to help the thawing process, then switch back to COOL.

Check Your Outdoor Unit

Walk outside and look at your condenser unit — the big metal box with the fan on top, usually sitting on a concrete pad next to the house. This unit is responsible for dumping heat from your home into the outdoor air. If it cannot do its job, the whole system suffers.

• Is it running? You should hear the fan spinning and the compressor humming. If the unit is completely silent, the issue may be electrical — a tripped breaker or a blown contactor relay.
• Is it clear of debris? Austin's live oaks, pecans, and crepe myrtles drop leaves, seed pods, and pollen that accumulate on and around the condenser. Grass clippings from mowing also pile up. The unit needs at least two feet of clearance on all sides for proper airflow. If it is packed with debris, hose it down gently from the inside out.
• Is the fan spinning? If the compressor is humming but the fan is not spinning, the fan motor or capacitor may have failed. Do not attempt to manually spin the fan — call an HVAC tech.
• Is there ice on the refrigerant lines? Look at the copper lines running from the outdoor unit to the indoor unit. If the larger line (the suction line) is covered in ice, you likely have a refrigerant leak or severe airflow restriction. Turn the system off and call a professional.

Check Your Vents and Returns

Walk through your house and check every supply vent and return air grille:

• Are any vents closed? Every vent should be open, even in rooms you do not use. Closing vents increases pressure in the ductwork, which forces the system to work harder and can cause duct leaks.
• Is furniture blocking any vents? A couch sitting directly over a floor vent or a dresser pushed against a wall vent blocks airflow to that room and reduces the system's overall efficiency.
• Are any return air grilles blocked by curtains, furniture, or rugs? The return is where air gets pulled back into the system to be cooled. Blocking it starves the system of airflow.

In older Austin neighborhoods like Brentwood, Crestview, and North Loop, many homes were built with undersized return air systems. They might have a single return in the hallway trying to serve the entire house. If that one return is blocked, the whole system loses airflow dramatically.

Check Your Breaker Panel

Your HVAC system uses two breakers in your electrical panel — one for the indoor air handler and one for the outdoor condenser. Sometimes one trips without the other.

• Find your breaker panel and look for the breakers labeled HVAC, AC, AIR HANDLER, or CONDENSER. They are usually 20-30 amp breakers.
• If either breaker is tripped (sitting in the middle position, not fully ON or OFF), switch it all the way OFF, wait 30 seconds, then switch it back ON.
• If the breaker trips again immediately, do not keep resetting it. A breaker that trips repeatedly is protecting your home from an electrical fault. Call a tech.

A tripped breaker is not always a serious problem. Power surges during Austin's summer storms can trip breakers without any underlying issue. But a breaker that repeatedly trips after reset signals a short circuit, ground fault, or failing motor that needs professional diagnosis.

When to Call a Professional

If you have checked the thermostat, replaced the filter, cleared the outdoor unit, verified your vents, and checked the breakers — and the system is still not cooling — it is time to call an HVAC professional. Here are the situations that need a licensed tech:

Refrigerant Leak

If the copper lines have ice on them, the system is blowing warm air despite running, or you hear a hissing or bubbling sound near the indoor unit, you may have a refrigerant leak. Refrigerant does not get "used up" — it circulates in a closed loop. If the level is low, there is a leak somewhere that needs to be found and repaired before the system is recharged.

Compressor Failure

If the outdoor unit hums loudly but the compressor does not kick on, or if you hear clicking and buzzing followed by the system shutting itself off, the compressor may be failing. The compressor is the most expensive component in your AC system, and a failed compressor on an older unit often means it is time to talk about replacement.

Ductwork Issues

If some rooms are cold and others are warm, or if you feel warm air leaking from joints in your attic ductwork, you have a duct problem. Disconnected or leaking ducts are common in Austin attics, especially in homes built in the 1980s and 1990s when duct sealing standards were less strict. You can lose 20-30 percent of your cooling capacity through duct leaks before the air ever reaches the vents in your rooms.

Electrical Issues

If the outdoor unit will not start at all, or if the air handler is completely silent, the problem may be electrical. A failed capacitor is one of the most common AC repairs in Austin — the capacitor stores the electrical charge that gets the compressor and fan motors spinning. When it fails, the motor hums but does not start, or the unit does not respond at all. Capacitors are inexpensive parts, but replacing one involves working with electrical components that hold a charge even when the power is off. Leave this to a tech.

A failed contactor relay can also prevent the outdoor unit from receiving the signal to turn on. The contactor is essentially a switch controlled by the thermostat. When it wears out or pits from electrical arcing, the signal does not pass through and the compressor stays off even though the thermostat is calling for cooling.

Frozen Evaporator Coil

If you see ice forming on the refrigerant lines or if the air handler is running but producing very little airflow, the evaporator coil may be frozen. This can happen from restricted airflow (clogged filter, blocked return), low refrigerant levels, or a failing blower motor. Turn the system to FAN ONLY to thaw the coil, which can take several hours. If it freezes again after thawing, a technician needs to find and fix the root cause.

How Austin's Heat Pushes Systems to Their Limit

We need to be honest about something: when Austin hits 105 degrees for days in a row, even a perfectly functioning AC system may struggle to maintain 72 inside. Most residential HVAC systems are designed to cool your home 20 degrees below the outdoor temperature. When it is 105 outside, the best your system can do might be 85 degrees indoors.

This does not mean your system is broken. It means it is running at maximum capacity. You can help it by keeping blinds and curtains closed on south and west-facing windows, running ceiling fans to circulate cooled air, avoiding oven use during peak afternoon heat, and making sure the attic is properly insulated so heat from above does not pour down into your living space.

Older Austin neighborhoods have additional challenges. Homes in Tarrytown, Zilker, and Bouldin Creek were built with ductwork designed for much smaller AC systems. When those homes were retrofitted with central AC in the 1970s or 1980s, the ductwork was often undersized for the new equipment. We see four-ton systems trying to push air through ductwork rated for two tons. The system has plenty of cooling capacity, but the ducts cannot move enough air to distribute it.

If your home consistently struggles to stay cool and your system is in good working order, a duct evaluation may be the missing piece. Adding return air, resizing supply runs, and properly sealing and insulating attic ductwork can transform how your system performs without replacing the equipment itself.

Preventive Maintenance That Reduces Emergency Calls

Most AC failures we see in Austin could have been prevented or caught early with basic annual maintenance. We recommend having your system professionally serviced every spring before the cooling season begins. A standard tune-up includes cleaning the outdoor condenser coil, checking refrigerant levels, testing electrical connections, lubricating motor bearings, and verifying thermostat calibration.

Between professional service visits, you can extend the life of your system by replacing the air filter every 30 days during the cooling season, keeping the area around your outdoor condenser clear of vegetation and debris, making sure supply vents and return grilles throughout the house stay open and unobstructed, and running your system in AUTO mode rather than keeping the fan running continuously.

A system that gets regular maintenance is far less likely to fail during the peak of an Austin summer. And when it does need repair, the issues tend to be smaller and cheaper because problems get caught before they cascade into major component failures.

The Bottom Line

Start with the simple fixes — thermostat, filter, outdoor unit, vents, breakers. These account for a surprising number of the AC calls we respond to in Austin. If those checks do not solve the problem, give us a call. We diagnose the actual issue before recommending repairs, and we will tell you straight whether a repair makes sense or whether your system has reached the point where replacement is the better path forward.