Cooling Emergency
AC Running But Not Cooling?
Your system is on, the fan is blowing, but the house keeps getting hotter. Here's what to check before you call.
What's Going On
Understanding the Problem
Your AC system is powered on and the fan is moving air, but the air coming out of the vents is warm or barely cool. The thermostat shows the temperature climbing instead of dropping. This is one of the most common AC problems in Houston, especially during summer when systems are working their hardest.
Diagnosis
Common Causes
1Dirty air filter
A clogged filter restricts airflow over the evaporator coil, which can cause the coil to freeze or simply prevent enough air from being cooled. This is the #1 cause of AC performance problems and the easiest to fix.
2Low refrigerant (Freon leak)
If your system is low on refrigerant, it can't absorb enough heat from the air. You'll notice the air coming out is barely cool instead of cold. Refrigerant doesn't get "used up" — if it's low, there's a leak somewhere.
3Dirty condenser coils (outdoor unit)
The outdoor unit dumps heat from your house into the outside air. If the coils are caked with dirt, grass clippings, or cottonwood, it can't release heat efficiently and your cooling suffers.
4Frozen evaporator coil
If the indoor coil ices over, air can't pass through it. This is usually caused by low airflow (dirty filter) or low refrigerant. You might see ice on the refrigerant lines near the indoor unit.
5Failing compressor
The compressor is the heart of the system — it circulates refrigerant. If it's weakening, the system runs but can't cool properly. This is a more serious repair and usually means the system is aging out.
6Thermostat issue
Sometimes the thermostat is set wrong (check that it's on COOL, not just FAN), the batteries are dying, or the temperature sensor is reading incorrectly.
DIY Troubleshooting
What You Can Try
Check and replace your air filter
Pull the filter out from the return vent or air handler. If you can't see light through it, it's too dirty. Replace it with the same size filter and give the system 30 minutes to recover.
Check the thermostat settings
Make sure it's set to COOL (not FAN ONLY or HEAT). Set it 5 degrees below current room temperature. If it has batteries, replace them.
Look at the outdoor unit
Go outside and check if the condenser fan is spinning. If the fan is running but you don't hear the compressor humming, the compressor may have failed. Also check if the unit is clogged with debris.
Check for ice on the lines
Look at the copper refrigerant lines running from your outdoor unit to the wall. If they're frosted or icy, turn the AC OFF and set the fan to ON to let the ice melt. Don't run the system until the ice is gone (usually 2–4 hours).
Check the breaker
Make sure the breaker for the AC hasn't tripped. The indoor and outdoor units often have separate breakers. If one tripped, the fan may run but the cooling won't work.
Know When to Call
When to Call a Pro
If you've checked the filter, thermostat, and breaker and the system still isn't cooling, it's time to call. Low refrigerant, compressor failure, and frozen coils all require a licensed technician with the right tools and training. In Houston's heat, every hour without cooling matters — don't wait.
Pro Tip
If your system is running non-stop but the house is only reaching 78–80°F on a 100°+ Houston day, that might actually be normal. Most residential AC systems are designed to cool about 20°F below outside temperature. If it's 105° outside, hitting 80° inside means the system is working correctly — it's just overwhelmed.
Need a Pro?
Services That Solve This
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