AC Not Cooling: Safe Checks Before You Call for Repair
Last updated Reviewed by Waseem Shahzad, Lead Technician
When the AC runs but the house will not cool on a humid Long Island afternoon, the cause is often airflow, a failed capacitor or a refrigerant problem. Check the simple things first. If the house is getting dangerously hot or something looks wrong, call (631) 414-7141. K2 answers 24/7.
Call 24/7: (631) 414-7141Smell gas or hear a carbon monoxide alarm? Leave the house first, then call 911 or the gas utility from outside.
Why is the AC running but not cooling?
The most common causes are a clogged filter, a frozen indoor coil, a dirty outdoor coil, a failed capacitor or contactor that stops the outdoor fan or compressor, a tripped breaker on the outdoor unit, or low refrigerant from a leak. Thermostat settings and closed vents cause some calls too.
- Airflow: a clogged filter or closed vents can freeze the indoor coil.
- Outdoor unit: a failed capacitor, contactor or fan motor, or a tripped breaker.
- Dirty outdoor coil: grass clippings, leaves and cottonwood block heat transfer.
- Refrigerant leak: low refrigerant means a leak, not refrigerant that was used up.
What can you safely check yourself?
Set the thermostat to Cool and a few degrees below room temperature. Replace a dirty filter, open vents, and check both breakers, indoor and outdoor. Look at the outdoor unit: the fan should spin and the coil should be clear. If the indoor coil or lines are iced, turn cooling off and let it thaw.
- Thermostat: Cool mode, set below room temperature, fresh batteries.
- Filter and vents: new filter, registers open, returns clear.
- Breakers: the indoor unit and the outdoor unit each have one; check the disconnect box by the outdoor unit too.
- Outdoor unit: clear leaves and debris away from it. Do not open panels or touch the fan.
- Ice: if the refrigerant lines or coil are frozen, set the system to Off with the fan On to thaw it, then call.
When is a cooling problem urgent?
Call right away when the house is getting dangerously hot with elderly residents, infants or anyone medically vulnerable at home. Also call for burning or electrical smells, a breaker that trips again, a humming outdoor unit with a fan that will not spin, or water leaking from an attic air handler.
- Heat risk for vulnerable people: tell us when you call.
- Burning or electrical smells, or repeated breaker trips.
- Humming but no fan outdoors, often a failed capacitor. Turn the system off so the compressor does not overheat.
- Water leaking from an air handler in an attic or above a finished ceiling.
- If you smell gas or a CO alarm sounds from any appliance, leave the house first and call 911 or the gas utility from outside.
What does K2 do on a no-cooling call?
We make the system safe, then check airflow, electrical components, the outdoor coil and refrigerant pressures to find the cause. You hear what failed and the price before any repair. Most common failures, such as capacitors and contactors, are fixed on the first visit with parts from the van.
On the phone we ask what the system is doing and what you have checked, then give you a time window and tell you if it changes. A refrigerant leak is found and repaired rather than just topped up. See AC repair for the full list of what we check.
Questions people ask
Can I just add refrigerant?
Refrigerant is not used up. If the system is low, it is leaking, and topping it up only buys time while the leak continues. The fix is to find and repair the leak, then charge the system correctly.
Why is my AC frozen in summer?
Usually poor airflow from a clogged filter or closed vents, or low refrigerant. Turn cooling off and run the fan to thaw the coil, replace the filter, and call if it freezes again.
The outdoor unit hums but the fan does not spin. What should I do?
Turn the system off at the thermostat so the compressor does not overheat, and call (631) 414-7141. A failed capacitor is the most common cause and is usually replaced on the first visit.
Need help now?
K2 answers 24/7 for homes within 15 miles of our shop at 60 S 2nd St, Unit V, Deer Park. You get a time window and the price before any repair.
Call 24/7: (631) 414-7141