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AC running but not cooling? What to check before you call

General home information from Prufloop. Updated October 28, 2026.

The short answer. When an AC runs but doesn't cool, check the basics first: thermostat set to Cool and below room temperature, a clean air filter, both breakers on (indoor unit and outdoor unit), and the outdoor unit running and clear of debris. If the outdoor fan isn't spinning, the lines are icy, or the system still won't cool, call an HVAC tech. Common causes are a failed capacitor, low refrigerant from a leak or a dirty coil.

Safety first. Don't open the outdoor unit's panels. Capacitors hold a charge even with the power off.

What you can safely check

Set the thermostat to Cool, a few degrees below room temperature, with the fan on Auto. Replace its batteries if it has them.
Replace a dirty air filter. A clogged filter is one of the most common causes of poor cooling.
Check the breakers for the indoor air handler and the outdoor unit, and the outdoor disconnect switch.
Look outside: is the fan spinning? Clear leaves, grass clippings and anything within about two feet of the unit.
Check for a full drain pan or a tripped float switch near the indoor unit, which can shut cooling off.
If you see ice on the lines or the indoor coil, turn cooling off and run the fan only (see frozen AC coil).

When to call a HVAC tech

The outdoor fan or compressor won't start, or you hear buzzing
Ice forms on the lines
The system cools a little but can't keep up
The breaker trips again after one reset

What a HVAC tech will usually do

Tests the capacitor, contactor and motors
Checks refrigerant pressures and looks for leaks
Cleans the coils and clears the condensate drain
Explains repair versus replacement on older systems

Asking an AI assistant to book it

Once Prufloop launches (planned for Q4 2026 around Charlotte), you'll be able to ask the AI assistant you use something like this, and it can book a verified pro at a posted price in a real open slot. This is how it's planned to work; no assistant is connected yet.

Example request. “My AC is running but blowing warm air and the outdoor fan isn't spinning. Book a licensed HVAC tech in Mooresville today or tomorrow at a posted diagnostic fee.”

Before a job is booked, you see the pro's posted price, including any trip or diagnostic fee. Anything extra needs your OK first. When the work is done, you confirm it's fixed with a quick text. That's Proof of Done™.

Questions

How cool should my house get?

A working system usually cools the air about 15 to 20 degrees between the return and the supply vents. On very hot, humid Charlotte afternoons, it may struggle to hold more than about 20 degrees below outdoor temperature.

Can I add refrigerant myself?

No. Refrigerant work requires an EPA Section 608 certified technician, and low refrigerant means there's a leak that needs finding.

Can my AI assistant book a HVAC tech for this through Prufloop?

Not yet. Prufloop is being built so the AI assistant you already use can book a verified HVAC tech at a posted price, starting with the Charlotte-area pilot planned for Q4 2026 in Mecklenburg, Union, Cabarrus, Iredell, Gaston and Lincoln counties in North Carolina, plus York and Lancaster counties in South Carolina. No AI assistant is connected yet.

Are you a Charlotte-area HVAC tech?

Free to join. Only pay on jobs completed: 10% on jobs under $2,500, less on bigger jobs, charged when the job is marked done. No lead fees. Founding pros get a guaranteed spot and founding terms locked for 24 months.

Secure your spot

How it works for pros