Why Your AC Isn't Cooling — and What to Check First

It's 102°F outside, the thermostat says 78°, and the house just won't get there. Before you assume the worst, know this: most "AC not cooling" calls we run in Leander come down to a handful of causes, and a couple of them you can rule out yourself in five minutes. This guide walks through the safe checks first, then the problems that genuinely need a technician — so you're never paying for something you didn't need.

First, what "not cooling" usually means

When an AC runs but doesn't cool, the system is almost always failing at one of three jobs: moving enough air, getting enough power, or moving heat with refrigerant. Narrowing it to one of those three is half the battle, and it tells you whether this is a quick fix or a real repair.

Safe checks you can do yourself (5 minutes)

None of these require tools or opening up equipment. If any one of them fixes it, you've saved a service call.

1. Check the thermostat
   Confirm it's set to Cool (not just “Fan”), the target is below room temp, and the batteries aren't dead. A thermostat left on “Fan On” blows room-temperature air and feels exactly like a broken AC.
2. Replace the air filter
   A clogged filter is the #1 cause we find. In a dusty Central Texas summer, a 1-inch filter can choke off airflow in 30–60 days. If it looks gray, swap it.
3. Look for ice
   If the indoor coil or the copper line is frosted, switch the system to Fan Only for an hour to thaw it. A frozen coil can't cool, and running it frozen risks the compressor.
4. Check the breakers
   An AC has two power sources — the indoor air handler and the outdoor unit. If the outdoor unit is silent, a tripped breaker or flipped disconnect is a common, harmless cause.
5. Clear the outdoor unit
   Pull weeds, leaves, and clippings off the condenser and give it two feet of breathing room. A smothered condenser can't dump heat.
6. Check the condensate drain
   Many systems shut cooling off on purpose when the drain clogs and the safety float trips. A wet-vac on the outside drain line can sometimes clear it.

When it's not a DIY fix — call a pro

These point to problems that need a licensed, EPA-certified technician. Trying to "fix" them yourself usually costs more in the end.

• It keeps freezing after a filter change. Repeated icing usually means low refrigerant (a leak) or a failing blower — both need diagnosis.
• The outdoor unit hums but the fan won't spin. Often a failed capacitor or contactor. Inexpensive parts, but live high-voltage work.
• You hear hissing or see oily residue on the lines. Classic refrigerant-leak signs. Refrigerant is regulated and a leak must be found and sealed, not just topped off.
• Burning smell, repeated breaker trips, or warm air from every vent. Stop and call — these can indicate electrical or compressor problems.

A quick note on refrigerant: if a company's first move is to "add a couple pounds of Freon" and send you on your way, be cautious. Low refrigerant means a leak. That's also why the 2025 R-454B refrigerant change matters — older R-410A is getting expensive, which shifts the repair-vs-replace math on leaky older systems.

How we approach it (and why honest beats fast)

MLD Services has run these calls across Leander, Cedar Park, Georgetown, Liberty Hill, and Round Rock since 2009. Our owner-led, repair-first philosophy is simple: we diagnose the actual cause, show you what we found, and quote a flat rate before any work starts. If a $300 repair will get you several more good years, we'll tell you that — we won't push a replacement you don't need. Every diagnosis is backed by our 100% Satisfaction and Clean Home guarantees and our Lifetime Workmanship Warranty, and we're a Factory-Authorized York dealer with NATE- and EPA-certified technicians (license TACLA37761C).

What to do next

If the safe checks above didn't bring the temperature down, don't keep running a struggling system in the heat — it can turn a small repair into a bigger one. A few honest next steps:

• Wondering whether to fix it or start fresh? Read Repair or Replace Your AC? for the exact rules we use.
• Bills creeping up along with the heat? See Why Your Summer Electric Bill Is So High.
• Got a repair or replacement quote from someone else? Get a free second opinion — we'll review it line by line, no pressure.

Or just call 512-528-4258. Same-day appointments are often available, and after-hours repair is too. You'll talk to a local team that would rather teach you than sell you.