It’s 2 PM on a Saturday in July. You just walked inside expecting that blast of cool air, but instead? Your house feels like an oven. The AC’s running, the thermostat says 72, but your living room is pushing 82. What gives?
Look, if your AC isn’t cooling, the usual suspects are clogged filters, low refrigerant, dirty coils, thermostat issues, or a failing compressor. The good news? Most of these problems are fixable—and some you can even troubleshoot yourself before calling a pro.
Quick Facts: Why Houston ACs Stop Cooling
- Clogged filters are number one: We see this constantly in Texas homes. Pet hair, pollen, and humidity make filters work overtime—change yours every 30-45 days, not quarterly.
- Dirty coils kill cooling power: Your outdoor unit pulls in cottonwood fluff, grass clippings, and Houston humidity. When coils get coated, heat transfer drops fast.
- Low refrigerant equals no cooling: If your AC runs nonstop but never cools, you probably have a leak. Adding refrigerant without fixing the leak is just a temporary band-aid.
- Duct problems are sneaky: If air feels cool at the vent but your house stays hot, you might have leaking ducts in that 140-degree attic.
- Frozen coils shut everything down: Ice on your refrigerant lines means airflow or refrigerant issues. Turn off the AC immediately—running it frozen damages the compressor.
- Compressor failure is worst-case: This is the heart of your system. If it fails and you’re out of warranty, replacement costs can justify buying a whole new unit.
Why Is My AC Not Cooling the House?
Alright, let’s break down the most common reasons—starting with the stuff we see every single day in Houston-area homes.
Dirty or Clogged Air Filters (The Number One Culprit)
This is the number one thing. Seriously. Airflow is everything for an AC, and when filters get packed with dust, pet hair, and that lovely Texas pollen, your system can’t pull enough air to cool it properly.
Signs this is your problem:
- Weak airflow from the vents
- Warm or room-temperature air blowing out
- Ice forming on your indoor coil
- Electric bill creeping up for no reason
The fix? Replace or clean the filter. And yeah, if you have dogs or cats—or if you live near The Heights where the pollen gets insane—you’re looking at new filters every 30-60 days. The box might say quarterly, but Texas doesn’t play by those rules.
Dirty Evaporator or Condenser Coils
Your AC has two sets of coils doing the heavy lifting:
- Evaporator coil (inside) — pulls heat out of your air
- Condenser coil (outside) — dumps that heat outdoors
When these get coated with dust, mildew, or grime, heat transfer tanks. The outdoor unit? We’ve seen them buried in cottonwood fluff, grass clippings, wasp nests—you name it. Inside, the evaporator coil stays damp from Houston humidity, so mold loves it.
The fix: Professional coil cleaning. You can rinse off the outdoor unit with a garden hose (gently), but for the indoor coil, call a tech. Adding UV lights inside your air handler helps prevent mold buildup too—worth considering if you’re dealing with this regularly.
Low Refrigerant or Refrigerant Leaks
Refrigerant (usually R-410A these days) is what actually absorbs the heat from your house. If levels drop, your AC can’t do its job. And here’s the thing—adding more refrigerant without fixing the leak is like filling a tire with a nail in it. Temporary fix at best.
Common signs of low refrigerant:
- AC runs constantly but never hits the set temperature
- Ice on the refrigerant lines (those copper pipes)
- Hissing or bubbling sounds near the coil or outdoor unit
- Utility bills through the roof
Causes? Could be installation errors, vibration cracks over time, or coil corrosion (Houston’s humidity accelerates this).
The fix: A tech has to find the leak, repair it, then recharge the system properly. Refrigerant work requires EPA certification—this is not DIY territory.
Blocked or Leaking Air Ducts
Here’s a sneaky one. If the air coming out of your vents feels cool but your house still won’t reach temperature, you probably have a duct issue.
In Houston, we see this all the time:
- Attic pests (rats, squirrels) chewing through ducts
- Ducts coming loose in 140-degree attics
- Crushed or disconnected flex ducts
- Poorly sealed joints bleeding cold air into the attic
The fix: Duct inspection and repair. Sealing leaks can improve your cooling and drop energy costs by 20 percent or more. Yeah, it’s worth it.
Thermostat or Sensor Problems
Sometimes the problem isn’t mechanical—it’s just the thermostat being weird.
Check these first:
- Thermostat is set to Cool (not Auto or Fan Only)
- Temperature setting is actually lower than room temp
- Batteries aren’t dead (yeah, we get calls for this)
- Sensor isn’t loose or sitting in direct sunlight
The fix: Replace batteries, move the thermostat if it’s in a hot spot, or upgrade to a smart thermostat that won’t give you grief.
Frozen Evaporator Coil
If your coil freezes up, cooling stops dead. Common causes:
- Clogged filters (yeah, back to filters again)
- Low refrigerant levels
- Closed supply or return vents
- Blower motor failing
The fix: Turn off the AC, switch the fan to On to help it thaw, and schedule service to figure out what caused it. Don’t just run it—you’ll wreck the compressor.
Compressor Failure (The Expensive One)
The compressor is basically the heart of your AC—it’s what circulates refrigerant between the indoor and outdoor units. When it dies, cooling dies with it.
Compressors fail because of:
- High electrical load (power surges, storms)
- Refrigerant problems (too low or too high)
- Overheating from dirty coils
- Just plain age
The fix: If you’re out of warranty, compressor replacement is expensive enough that you might be better off replacing the whole system. Not gonna lie—it’s a tough call, but your tech can help you weigh the options.
What Makes AC Cooling Problems Worse
Several things determine how bad—and how expensive—your cooling problem gets.
Age of Your System
Systems over 10-12 years old are way more likely to spring refrigerant leaks, develop coil corrosion, and have compressor issues. If yours is pushing 15, it might be time to think about replacement.
Severity of Airflow Blockages
A twenty-dollar filter swap might fix everything—or you might need a full coil cleaning and duct repair. It depends on how long the problem has been ignored.
Type of Refrigerant
Older units using R-22 (which is phased out) can cost a fortune to recharge. If that’s you, replacement might actually be cheaper long-term.
Texas Attic Conditions
Houston attics regularly hit 140 degrees in summer. That accelerates duct damage, component wear, and insulation breakdown. It’s brutal up there.
Step-by-Step: Troubleshoot Before Calling
Alright, here’s what to do if your AC stops cooling.
Start with the Easy Stuff
- Replace the air filter
- Make sure the thermostat is on Cool
- Check that the outdoor unit has power and isn’t buried in debris
- Open all your supply vents
Look for Obvious Problems
- Ice on the copper refrigerant lines
- Dirty or blocked outdoor condenser
- Weak airflow from vents
- Water pooling around the indoor unit
If Easy Fixes Do Not Work, Call a Pro
Refrigerant issues, electrical failures, and duct repairs need licensed HVAC expertise. Don’t mess around with these—they’re safety risks.
Schedule Routine Maintenance
Twice-yearly tune-ups are honestly the best way to prevent cooling failures. Techs catch refrigerant leaks and dirty coils before they turn into expensive emergencies.
Houston HVAC Reality Check
Texas heat waves are getting longer and hotter. We’re seeing more homeowners schedule early spring maintenance to avoid mid-summer breakdowns—because nobody wants to wait three days for service when it’s 103 outside.
High-efficiency systems with better humidity control are becoming the standard in new installs, especially in Katy, Sugar Land, and The Woodlands. They cost more upfront but save serious money on electricity.
FAQ
Why is my AC running but not cooling?
Usually clogged filters, low refrigerant, dirty coils, or a thermostat issue. Start with the filter—that fixes it like 40 percent of the time.
Can low refrigerant damage my AC?
Yep. Running on low refrigerant can freeze the coil or strain the compressor. Both are expensive problems you want to avoid.
Should I turn off my AC if it is frozen?
Absolutely. Turn off cooling but keep the fan running to melt the ice. Then call a tech to figure out why it froze.
How often should I replace my AC filter?
Every 30-60 days in Texas. Pets, pollen, and humidity make filters work way harder here than in other climates.
When should I consider replacing my AC?
If it’s 12-15 years old and needs a major repair (compressor, coil), replacement usually makes more financial sense.
John Moore HVAC Services: Your Houston AC Experts
If your AC isn’t cooling and Texas heat isn’t waiting, John Moore HVAC Services has your back. Our licensed technicians can diagnose refrigerant issues, clean coils, repair ductwork, or get your system running safely and efficiently again.
We’ve been serving the greater Houston area for over 50 years, and we know exactly what local systems go through. Whether you’re in Memorial, The Heights, Katy, or Pearland, we’re ready to help. Give us a call.
