AC Not Cooling in Katy, TX? Causes & Fixes | Katy 24 Hour AC Repair

AC running but not cooling your Katy, TX home? Here’s exactly why, ranked by likelihood, and what to check before calling for repair. Call (346) 480-4090.

AC Not Cooling in Katy, TX — Causes and What to Do

When your AC runs but the house isn’t cooling, the cause is almost always one of five things: a thermostat set incorrectly, restricted airflow, a low refrigerant charge, a frozen evaporator coil, or a failing compressor. In Katy’s climate specifically, restricted airflow and low refrigerant are by far the most common causes we find, because humidity and heat load push these components harder here than in most of the country.

Most Likely Causes, Ranked

  • A dirty or clogged air filter restricts airflow across the evaporator coil, reducing cooling capacity and, if bad enough, causing the coil to freeze
  • Low refrigerant charge usually from a slow leak, common in older coils affected by formicary corrosion, a pinhole-style corrosion pattern distinct from ordinary rust
  • A frozen evaporator coil is often a downstream effect of the two causes above, blocking airflow entirely once ice builds up
  • Closed or blocked supply vents and closed interior doors reduce airflow return, straining the system unevenly
  • Failing capacitor, compressor, or fan motor struggling to start or run at full capacity
  • Ductwork leaks cool air escaping into the attic before it reaches the room, especially in older attic-run duct systems
AC Not Cooling

What to Check Before Calling

Confirm the thermostat is set to “cool,” not “fan only,” and that the set temperature is below the current room temperature. Check whether the air filter is visibly gray or clogged if so, replace it and give the system 30 minutes before judging results. Walk the house and confirm no supply vents are closed or blocked by furniture. If none of that resolves it, or if you see ice on the indoor coil or refrigerant lines, turn the system off at the thermostat and call rather than running it further a frozen system that keeps running can damage the compressor.

How We Diagnose a No-Cooling Call

We run a temperature-drop test across the evaporator coil a healthy Texas system should show roughly a 15 to 20 degree drop between the return air and the supply air. A reading well below that, combined with normal airflow, usually points to low refrigerant. Normal refrigerant pressure with poor airflow points back to a filter, duct, or blower issue instead. We test rather than guess, because “not cooling” has several unrelated root causes that require different fixes.

Why This Is More Common in Katy Than Elsewhere

Katy’s combination of extended run time nine to ten months of near-daily cooling and high humidity accelerates both the airflow-restriction and refrigerant-leak causes specifically. Homes in Elyson and Tamarron with newer, builder-grade coils often see this symptom by year three as coils begin fouling from humidity exposure, while older systems in Cinco Ranch and Kelliwood more often show it as a slow refrigerant leak in aging copper lines.

Repair Cost for This Issue

Cost depends entirely on which cause applies. A filter or airflow fix is often free to low-cost if it’s simply a filter change; a capacitor replacement typically runs $150 to $350; refrigerant leak repair with recharge runs $200 to $600 depending on the leak’s location and severity; a full compressor issue can run into the $1,000-plus range. This wide range is exactly why we diagnose before quoting rather than giving a flat “AC not cooling” price over the phone the fix and the cost genuinely depend on which of the causes above applies to your system.

When This Symptom Overlaps With Others

“Not cooling” is often the entry point to a more specific symptom once we look closer a system not cooling because of ice on the coil is really a frozen-unit issue with its own thawing process, while a system not cooling because it’s blowing warm air at normal airflow points more directly toward refrigerant or compressor. If you’re also seeing ice, warm air specifically, or unusual noise alongside the lack of cooling, mentioning that when you call helps us bring the right parts on the first visit.

Frequently Asked Questions

The most common causes are restricted airflow from a dirty filter, low refrigerant from a slow leak, or a frozen evaporator coil often one causing the next. A technician can identify the specific cause with a temperature-drop test and refrigerant pressure check.

Yes. A severely clogged filter restricts airflow across the evaporator coil enough to drop cooling capacity noticeably, and in more extreme cases can cause the coil to ice over entirely, cutting off airflow completely.

If you see ice on the coil or lines, turn the system off at the thermostat rather than continuing to run it a frozen system that keeps running risks damaging the compressor, turning a moderate repair into a major one.

It depends on the cause running a system with a frozen coil or an overheating compressor for an extended period risks turning a moderate repair into a major one. If basic checks (thermostat setting, filter, vents) don’t resolve it within a short time, it’s worth calling rather than continuing to run the system.

The diagnostic process is the same regardless of brand Trane, Carrier, Lennox, Goodman, Rheem, and others all rely on the same fundamental refrigeration cycle, so the same temperature-drop and pressure testing applies. Brand mainly affects parts availability and specific access procedures, not the underlying diagnostic logic.

Preventing This From Happening Again

Most repeat “not cooling” calls trace back to skipped filter changes or a maintenance visit that got pushed off. A spring tune-up that includes a refrigerant check and temperature-drop test catches a slow leak or a marginal capacitor months before it turns into a full no-cooling event on a 100-degree afternoon. Given how many of these causes are catchable in advance, preventive maintenance is genuinely the more cost-effective path compared to repeatedly repairing the same underlying issue after it fails.

What Our Technicians Bring to a No-Cooling Call

Because the causes above range from a simple filter swap to a compressor issue, our trucks carry the full range of commonly needed parts capacitors, contactors, common motor sizes, and refrigerant for the Katy market specifically, based on what we see fail most often in this climate. This is why the majority of no-cooling calls are resolved in a single visit rather than requiring a follow-up appointment once a part is sourced.