If your AC is running but the house won't cool in Houston, the usual causes are a clogged condensate drain that tripped the safety switch, a clogged filter, a dirty outdoor coil, a weak capacitor, low refrigerant, or a frozen indoor coil. Houston's humidity makes the drain problem far more common than anywhere else in Texas. Check the thermostat, filter, breaker, and the attic drain pan first. If the outdoor unit runs but the air at the vents is warm, turn the system off and call a licensed tech before a cheap repair turns into a compressor.
The five-minute checks before you call anyone
Thermostat. COOL mode, setpoint below room temperature, fan on AUTO. A fan on ON circulates humid air between cycles and makes a Houston house feel worse.
Attic drain pan. Look at the air handler. Water in the pan means the condensate drain is clogged with algae and the float switch shut the system off. It looks like a dead AC. Clearing the line at the outdoor end with a wet/dry vacuum usually restores cooling.
Filter, breaker, outdoor unit. Replace a loaded filter, reset a tripped breaker once, and confirm the outdoor fan spins. If it hums without spinning, stop; that's a capacitor for a tech.
Why Houston systems stop cooling
Moisture. Nine months of humid cooling load means the indoor coil pulls gallons of water a day. Drain lines clog, pans overflow, and near the bay, coils and contactors corrode.
Heat and debris. Outdoor coils packed with pollen, grass clippings, and post-storm debris can't reject heat. Capacitors weaken through the summer and quit in August.
Power flickers. After a CenterPoint outage or a storm, a system that won't restart often has a tripped breaker, a blown low-voltage fuse, or a capacitor that didn't survive the surge.
When to shut it off and get a tech out today
Turn the system off if the outdoor unit runs but the indoor air is warm, if you see ice on the copper lines, or if it short-cycles. Continuing to run it risks the compressor.
In peak season, Houston contractors triage no-cool calls. Say it's a no-cool and mention any elderly residents, infants, or medical conditions in the home.
LocalFixQuotes is not a contractor. We match Houston homeowners with independent, TDLR-licensed HVAC contractors who diagnose and quote the repair. It's free and there's no obligation to hire.
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