Why is my AC running but not cooling?
Last updated September 2026
Quick answer
Most often it's something simple: the thermostat setting, a clogged air filter, a tripped breaker for the outdoor unit, or a blocked outdoor unit. If those check out, or you see ice, hear odd noises, or the outdoor fan isn't spinning, turn the system off and call a licensed HVAC company.
1. Check the thermostat
Make sure it's set to Cool, the temperature is set below the room temperature, and the fan is on Auto. If the fan is set to On, it blows air even when the system isn't cooling, which can feel like the AC "isn't working." Replace the batteries if the screen is blank or dim.
2. Look at the air filter
A clogged filter blocks airflow, so the system runs without moving much cool air. It can even make the indoor coil freeze. If the filter looks gray or dusty, replace it. In Houston, with the AC running most of the year, check it every month.
3. Check the breakers and the outdoor unit
The outdoor unit usually has its own breaker in the panel and a shut-off box on the wall next to it. If the indoor fan runs but the outdoor unit is silent, a tripped breaker is a common cause. Reset it once; if it trips again, stop and call a pro. Also clear leaves, grass and anything stacked against the outdoor unit so it can release heat.
4. Watch for ice or water
Ice on the copper line outside or on the indoor coil means the system should be turned off so it can thaw. Leave the fan on to speed it up. Water around the indoor unit, or a system that shuts itself off, can point to a clogged drain line. In attic installs, that can leak into the ceiling below, so don't wait on it.
5. Know when to call a pro
- The outdoor fan isn't spinning, or the unit hums or buzzes without starting
- Ice keeps coming back after it thaws
- A breaker trips again after one reset
- You smell burning, or hear grinding or squealing
- It might need refrigerant: that must be done by an EPA 608 certified technician, and low refrigerant means there's a leak to fix
Before work starts, ask for the company's Texas ACR license number and a written estimate.
Find a licensed AC repair pro near you
- AC repair in Houston
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AC not cooling? Common questions
Can I add refrigerant myself?
No. Refrigerant work requires an EPA 608 certified technician. Low refrigerant also means there is a leak, which needs to be found and fixed.
Should I keep running the AC if it isn't cooling?
If you see ice, hear grinding or buzzing, or the outdoor fan isn't spinning, turn the system off. Running it can turn a small repair into a big one.
What should I tell the company when I call?
Say what you checked, whether the outdoor unit and its fan are running, whether you saw ice or water, and how long it has been happening.