AC Running but Not Cooling? What to Check First
The safe checks that fix many cooling problems in minutes, what ice and warm air are telling you, and when it is time to call.
Start with the easy things
- Thermostat. Set to Cool, fan on Auto, set temperature several degrees below the room. Replace the batteries.
- Breakers. Central air uses two breakers: one for the indoor furnace or air handler and a larger double breaker for the outdoor unit. There is usually also a disconnect box on the wall next to the outdoor unit.
- Filter. A clogged filter is the most common cause of weak airflow and frozen coils.
- Vents. Make sure supply and return vents are open and not blocked by furniture or rugs.
- Outdoor unit. It should be running when the system is on, with the fan spinning and warm air blowing off the top.
If you see ice
Ice on the large copper line at the outdoor unit, or frost on the indoor coil, means the coil is getting too cold. That is almost always caused by poor airflow, from a dirty filter, closed vents or a weak blower, or by low refrigerant from a leak.
Turn the system to Off and the fan to On for a few hours to melt the ice. Put a towel near the furnace in case the drain pan overflows. Replace the filter. Then turn cooling back on. If it freezes again within a day, call us. Running a frozen system can damage the compressor, which is the most expensive part of the unit.
Frozen lines are one of our most common July calls. About half the time it is a filter that has not been changed since spring. The other half, it is a slow refrigerant leak, often at a corroded coil or a fitting, and the only real fix is finding the leak, not just adding refrigerant.
If the outdoor unit hums but will not start
A humming outdoor unit with a fan that does not spin, or a compressor that clicks on and off, usually has a failed capacitor. That is one of the most common and least expensive AC repairs. Turn the system off at the thermostat so the compressor does not overheat trying to start, and call. Please do not poke the fan blades with a stick. The capacitor stores enough energy to hurt you.
Still hot inside?
Call and tell us what the outdoor unit is doing. We can often narrow it down on the phone.
If it runs but the house stays warm
Check the outdoor coil. Grass clippings, dryer lint and cottonwood fluff can coat it so thoroughly that it cannot shed heat. With the power off at the disconnect, gently rinse the coil from the outside with a garden hose, never a pressure washer, then restart.
In the neighborhoods along the Licking River in Newark and Heath, early summer cottonwood season is hard on air conditioners. The fluff gets drawn into the coil and mats down. A unit that seems to be failing often just needs a thorough coil cleaning.
Also consider the weather. On a humid 92-degree day, a correctly sized system may only hold the house around 75 to 78 degrees and run nearly nonstop. That is normal. Struggling to reach 80 on an 85-degree day is not.
Water around the furnace
Your air conditioner pulls water out of the air and drains it away. If the drain line clogs with algae, water can back up and overflow, or trip a float switch that shuts the system off. On many systems, a cup of distilled white vinegar poured into the drain access tee each spring keeps the line clear.
When to call
Call (740) 527-0222 if the checks above do not solve it, if the system keeps freezing, if breakers keep tripping, or if you hear grinding, screeching or loud clanking. Our AC repair page explains what we check and what common repairs cost. If your system is over twelve years old, our repair or replace guide can help you decide whether fixing it makes sense.
AC troubleshooting questions
Why is my AC running but not cooling?
The most common causes are a dirty filter, a dirty outdoor coil, a failed capacitor, or low refrigerant from a leak. Start with the filter and the outdoor coil, then call if it still will not cool.
Is it normal for my AC to run all day?
On very hot, humid days a properly sized system can run nearly continuously. If it runs all day in mild weather or never gets the house below 80, something is wrong.
Can I add refrigerant myself?
No. Refrigerant handling requires EPA certification, and if the system is low it has a leak that needs to be found and repaired.
Why is water leaking from my furnace in summer?
Your AC produces condensation that drains through a line near the furnace. A clogged drain line or a failed condensate pump is the usual cause of leaks.
How cold should the air from my vents be?
Supply air is typically 15 to 20 degrees cooler than the air going into the return. A smaller difference usually points to a charge, airflow or coil problem.
Next steps
AC Repair
Warm air, frozen lines or a unit that will not start, fixed right the first time.
Learn more →AC Replacement
New central air sized with a real load calculation, not a guess.
Learn more →Heat Pumps
Cold-climate and dual-fuel heat pumps, repaired and installed for Ohio winters.
Learn more →Tune-Ups & Maintenance
Fall furnace and spring AC tune-ups that catch small problems early.
Learn more →Get your cooling back
Calling is the fastest way to get on the schedule. Tell us what the system is doing and we will tell you what it probably is, what it probably costs and when we can be there.
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