Running but not cooling: the eight causes, in order
If the indoor blower is running but the air isn't cold, here's what we find most often in Houston, in rough order: a dirty filter or coil, a thermostat that's mis-set or failing, a run capacitor that's out of tolerance, low refrigerant from a leak, a dirty or failed condenser fan, a stuck contactor, duct leakage in the attic, and finally a failing compressor. The first three account for the majority of calls.
The 60-second checks you can do yourself
Before calling, walk outside and make sure the condenser fan is spinning and the top of the unit isn't hot enough to cook an egg. Check the air filter — if it's gray and clogged, replace it and wait an hour. Confirm the thermostat is set to 'cool' and 'auto,' not 'fan on.' These checks cost nothing and rule out the simple stuff immediately.
Why low airflow feels like low cooling
An AC that can't move air can't cool air. Collapsed flex duct, a dirty evaporator coil, closed registers, or a dying blower motor all starve the system of airflow and freeze the coil. Half of 'the AC isn't cooling' calls turn out to be an airflow problem, not a refrigerant problem — and they're usually a fraction of the price to fix.
When low refrigerant is the real answer
If the airflow is fine but the air still isn't cold, the refrigerant charge is the next suspect. Symptoms are an ice line on the suction pipe, a hissing sound at the indoor coil, or long run times with no temperature drop. This is a sealed-system job for a licensed tech — your home has no 'add refrigerant' port and topping off without a leak search is both illegal and wasteful.
Frequently Asked Questions
Why is my AC running but not cooling the house?
The most common causes are a dirty filter or coil, a failing capacitor, low refrigerant, or an airflow problem. A tech can isolate it in about 20 minutes with a gauge set and an amp clamp.
How do I know if it's low refrigerant vs. airflow?
If airflow from the vents is strong but the air is warm, suspect the charge. If airflow is weak and the coil is iced over, suspect airflow. Both need a licensed technician to confirm.
HVAC247PRO is a licensed Texas HVAC contractor (TACLB00105442E and TACLA95904E) serving the Houston metro 24/7. If your system is showing any of the signs above, call (346) 451-1559 or book an inspection online and a technician will be at your door the same day.