Your system is on — the fan is spinning, the outdoor unit is humming — but the house won't cool. In Texas the usual causes are a frozen coil, a clogged filter, low refrigerant, a thermostat set to "fan on," or leaky attic ductwork. Some are five-minute checks you can do right now. Others need a technician.
"Running but not cooling" means the electrical side is working but heat isn't being removed from your home — or the cold air isn't reaching your rooms. Start by checking what kind of air is coming out of the vents: warm, weak, or cold-but-not-enough. That single detail points you toward the cause faster than anything else.
Same-day diagnosis available in Spring TX 77386 & 77388. Diagnostic fee waived with qualifying repair.
The type of air at your registers narrows the problem down immediately:
North Houston systems run 9–10 months a year and routinely face 100°F+ afternoons. On the hottest days, even a healthy, correctly sized system may only hold the house 20–25°F below the outdoor temperature — so "can't get below 80°" on a 105° day isn't always a fault.
Texas conditions also accelerate the real faults: attic duct temperatures of 140–160°F stress the whole system, and cottonwood season packs condenser coils every April and May. If your system genuinely isn't keeping up on a normal day, one of the causes above is in play.
Struggling only on the very hottest afternoons? That specific scenario is covered in AC Not Cooling Below 80°F — capacity limits vs. actual faults.
| What you're seeing | Most likely cause | DIY or Pro |
|---|---|---|
| Warm air, outdoor fan running | Low refrigerant / dirty condenser | Pro |
| Weak airflow, some cool air | Clogged filter / frozen coil | DIY → Pro |
| Ice on lines or indoor coil | Frozen coil (airflow or refrigerant) | DIY thaw → Pro |
| Cold air, rooms still warm, runs nonstop | Duct leaks / undersized / extreme heat | Pro |
| Room-temp air only between cycles | Thermostat fan set to ON | DIY |
| Runs but barely cools, hard starts | Weak capacitor / compressor | Pro |
Rated 5.0 · 700+ Google reviews · Read all reviews
"AC was running all day and the house just kept getting hotter. Turned out to be a frozen coil from a filter nobody had changed in a year. Fixed same day, explained everything."— Spring TX homeowner, 77386
"System ran nonstop but never cooled the upstairs. They found duct leaks in the attic instead of just selling me a new unit. Honest crew."— Klein area, 77388
"Blowing warm air on a 102° day. Low on refrigerant from a leak — they found it, sealed it, and had us cool again by evening."— Harmony, Spring TX
A system that runs nonstop without reaching the setpoint is usually losing cooling capacity or losing the cooled air before it reaches your rooms. The most common Texas causes are a clogged filter or frozen coil restricting airflow, low refrigerant from a leak, a dirty condenser coil that can't reject heat, or leaky attic ductwork. On the hottest afternoons, an undersized or aging system may simply not be able to keep up. A diagnostic identifies which one it is.
Yes — if you see ice on the refrigerant lines or indoor coil, or water pooling around the indoor unit, turn the system OFF right away. Running a frozen system can damage the compressor, which is one of the most expensive repairs on the unit. Set the fan to ON to help it thaw, then have the cause diagnosed. If there's no ice and the air is simply warm, it's safe to keep troubleshooting, but a system that runs for hours without cooling should be checked promptly in Texas heat.
Warm air with the outdoor unit running points to heat not being rejected outside — most often low refrigerant from a leak, a dirty condenser coil, or a compressor running at reduced capacity. Before calling, confirm the thermostat is set to COOL and the fan is on AUTO rather than ON, since "ON" pushes room-temperature air between cooling cycles and mimics this symptom.
Yes. A clogged filter is one of the most common causes of weak cooling in Texas homes. It restricts airflow across the evaporator coil, which drops cooling output and can cause the coil to freeze over — at which point the system runs but blows little or no cold air. Replacing a packed filter and letting the system recover for an hour resolves a surprising number of "not cooling" calls.
Possibly. A weak run capacitor lets the compressor and fan run at reduced capacity, so the system runs but barely cools and may hard-start. It's cheap to fix and easy to misdiagnose — the full signs, testing, and cost are covered in the AC capacitor guide.
1827 Riley Fuzzel Rd Suite C, Spring TX 77386
Serving Harmony, Benders Landing, Legends Ranch, Imperial Oaks, Spring Trails, The Woodlands.
19507 Wied Rd Suite B, Spring TX 77388
Serving Klein, Champion Forest, Vintage Park, Gleannloch Farms, Tomball, Cypress.
