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Why is my AC running but not cooling in the Texas summer?
The five most common reasons an AC runs but won't cool in Texas summers are: dirty air filter, frozen evaporator coil, low refrigerant from a leak, failed capacitor, and outdoor coil clogged with cottonwood and pollen. Most are diagnosable in under 15 minutes.
What this means
"My AC is running but it's not cold" is one of the most common service calls we get from June through September in Austin. It almost always means the unit is consuming electricity but failing somewhere in the refrigeration cycle: either refrigerant isn't absorbing heat (low charge, frozen coil), heat isn't being expelled (dirty condenser, fan failure), or air isn't moving through the home (filter, blower, or duct issue). The good news: most causes are diagnosable and fixable same-day.
When this applies to Austin homes
Act immediately if: indoor temperature is climbing into the 80s+, the supply vents feel cool but not cold, you hear the outdoor unit running but the air handler is silent (or vice versa), or you see ice on the refrigerant lines near the outdoor unit. Turn the system off if you spot ice — running a frozen system damages the compressor. Then check the filter, give the coil 2–3 hours to thaw, and call for service if it freezes up again.
Warning signs & common mistakes
- Dirty air filter (most common): a clogged filter starves the blower of airflow, dropping coil temperature until it freezes. A frozen coil can't absorb heat — the air going to your vents is just being recirculated.
- Frozen evaporator coil: caused by low refrigerant, dirty filter, or restricted airflow. Looks like an ice block on the indoor coil or refrigerant line.
- Low refrigerant from a leak: refrigerant doesn't "run out" — it leaks. Common leak points in Texas: evaporator coil pinholes (formicary corrosion), line set fittings, and Schrader valves.
- Failed run capacitor: the outdoor fan won't spin or the compressor hums but doesn't start. $150–$300 fix.
- Cottonwood / pollen on outdoor coil: Central Texas spring and fall coat outdoor coils with debris. Insulated coils can't reject heat.
- Thermostat in heat mode or wrong batteries: always check first. Embarrassing, but it happens.
How Cheap Cold Air handles this
Our techs run the same diagnostic sequence on every "AC not cooling" call: thermostat → filter → indoor coil temp differential → outdoor coil cleanliness → refrigerant pressures → electrical components. About 30% of our summer no-cool calls are fixed in under 15 minutes for under $200 (filter, capacitor, thermostat). Another 40% are refrigerant or coil issues in the $400–$900 range. The remaining 30% are major component failures — compressor, blower motor, or system age — that require the repair-vs-replace conversation. We diagnose first and quote in writing before doing any work.
What to do next
If you've checked the filter and thermostat and the system still isn't cooling, turn the system off, give the indoor coil time to thaw if there's ice, and call us. Same-day diagnostic visits across Austin, Round Rock, Cedar Park, Georgetown, and Lakeway.
Related services
Frequently asked questions
Why is ice forming on my AC line?
Ice on the refrigerant line almost always means either a dirty/clogged filter restricting airflow, or low refrigerant from a leak. Both cause the evaporator coil to drop below freezing instead of the normal 40–50°F. Turn the system off, replace the filter, let it thaw for 2–3 hours, then run it again. If it freezes back up, you have a refrigerant leak that needs professional diagnosis.
How do I know if my AC has a refrigerant leak?
Signs include: ice on the refrigerant line, weak airflow that's only slightly cool, longer-than-normal cooling cycles, an oily residue at fittings, or a hissing sound near the indoor coil. The only way to confirm is with a leak-detection test — refrigerant is invisible. If a tech tells you the system 'needs more refrigerant' without finding the leak first, get a second opinion.
Can I clean my outdoor AC unit myself?
Yes — and you should, once a year in Central Texas. Turn off power at the disconnect, gently spray the fins from the inside out with a garden hose (not a pressure washer — fins bend easily), and clear debris from the base. Avoid spraying the electrical components on top. Don't open up the unit or touch refrigerant lines — that's tech territory.
Why is my AC blowing warm air in the afternoon but cool in the morning?
Two common causes in Texas: the system is undersized for the home's load (especially with afternoon sun on west-facing rooms), or the refrigerant charge is borderline — fine in mild morning conditions, inadequate when the load peaks. Both are diagnosable with a proper load calculation and refrigerant charge check.
Methodology: Diagnostic sequence pulled directly from the bench protocol our techs run on every no-cool call in the Austin metro. Failure-mode frequency reflects our internal service-call data across multiple Texas cooling seasons.