Do this now
- Confirm the thermostat is set to cool and below room temperature.
- Replace the air filter if it is dirty — this is the most common cause.
- Check the breakers for both the indoor unit and the outdoor unit, and the outdoor disconnect switch.
- Clear leaves, grass and debris from around the outdoor unit and make sure supply and return vents indoors are open.
- If you see ice on the indoor coil or the copper lines, turn the system off and run only the fan to thaw it.
- If it still does not cool, call an HVAC contractor rather than running it — operating a system that is frozen or low on refrigerant can damage the compressor.
What usually causes it
- A clogged filter or blocked vents restricting airflow
- A dirty outdoor coil that cannot shed heat
- Low refrigerant from a leak
- A failed capacitor or contactor in the outdoor unit
- A clogged condensate drain that has tripped a safety switch
What a professional will do
A technician measures temperatures and refrigerant pressures, tests the electrical components, and inspects both coils and the drain. If refrigerant is low, the leak should be found and repaired rather than simply topped off, and only a certified technician may handle refrigerant.
How to prevent it
- Change filters regularly through the cooling season
- Keep two feet of clearance around the outdoor unit and rinse the coil gently each spring
- Have the system checked in spring, before the first heat wave
- Keep the condensate drain clear
Rules and paperwork in Pennsylvania
- Pennsylvania’s Home Improvement Consumer Protection Act requires most contractors who perform home improvements to register with the Attorney General’s office and to give you a written contract for any job over $500. The registration number belongs on the estimate and the contract — ask for it.
- Technicians who handle refrigerant must hold EPA Section 608 certification under the Clean Air Act.
- Pennsylvania does not issue a statewide license for this trade. Some municipalities register or license it locally, which is one reason to confirm requirements with your own municipality.
Sources: Pennsylvania Office of Attorney General — Home Improvement Consumer Protection Act; U.S. EPA — Section 608 Technician Certification; Pennsylvania Department of Labor & Industry. Rules change — confirm current requirements with the agency and with your municipality.
Frequently asked questions
Why is there ice on my air conditioner?
Ice forms when airflow is too low or refrigerant is low. Turn the system off, let it thaw with the fan running, change the filter, and have it checked if it freezes again.
Can I add refrigerant myself?
No. Handling refrigerant requires EPA Section 608 certification, and a system that is low has a leak that needs to be found.
Why is water leaking from the indoor unit?
The condensate drain is probably clogged. Turn the system off to prevent water damage and have the drain cleared.
Go deeper
Our full heating & cooling guide covers how the work is done, what affects the price, and what to ask before you hire, and there is more on ac repair.
Heating & Cooling help by town
Related problems
This guide is general information, not a substitute for a professional assessing your home. If you are unsure whether something is safe, treat it as if it is not.