Start here
Quick, low-risk steps
- Move anyone at risk of heat illness to a cool location.
- Confirm the thermostat is set to 'cool' and the temperature is below room temperature.
- Check the air filter and replace it if it's visibly dirty.
- Look for ice on the indoor or outdoor unit and turn the system off if you see any.
- Write down the unit's model number and any error codes displayed.
Start With Safety and Simple Checks
In Phoenix, an AC that runs without cooling can quickly become dangerous. If anyone in your home is elderly, very young, or has a health condition, move them to a cooled space right away. Then, do a few basic checks that don't require tools or touching electrical parts.
Make sure your thermostat is set to 'cool' and the fan is on 'auto.' A wrong setting is a common cause. Also, look at your air filter. A clogged filter can block airflow and cause the system to freeze up or lose cooling.
- Move vulnerable people to a safe, cool location if needed.
- Check thermostat mode and temperature setting.
- Inspect the air filter and replace if dirty.
- Listen for unusual sounds like hissing or clanking.
- Do not open any access panels or touch refrigerant lines.
What Might Be Wrong
Several issues can cause an AC to run without cooling. The indoor coil might be frozen, which often happens due to low airflow or a refrigerant problem. If you see ice on the indoor or outdoor unit, turn the system off to let it thaw and call a professional.
A refrigerant leak is another possibility, but you cannot see or fix this yourself. Only EPA-certified technicians can handle refrigerant. Other causes include a failed compressor, a bad capacitor, or a tripped breaker. These all require a trained eye and proper tools.
- Frozen indoor coil (turn system off if ice is visible).
- Refrigerant leak (requires EPA-certified technician).
- Compressor or capacitor failure.
- Electrical issue such as a tripped breaker.
- Blocked or dirty outdoor condenser coil.
What to Document Before Calling a Pro
Before you call a contractor, gather information that will help them diagnose the problem faster. Write down the make and model of your unit, usually found on a label on the outdoor condenser. Also note any error codes flashing on the thermostat or control board.
Describe what you observed: Is the outdoor unit running? Is the indoor fan blowing? Is the air lukewarm or warm? This evidence helps the technician come prepared with the right parts and tools, potentially saving you time and money.
- Record the unit's make and model number.
- Note any error codes from the thermostat or unit.
- Describe whether the outdoor unit is running and if the fan is spinning.
- Check if the air from vents is warm, cool, or room temperature.
- Mention any recent changes or repairs to the system.
Questions to Ask a Licensed Contractor
When you call an HVAC contractor, ask about their diagnostic process and fees. A reputable company will explain what they check and give you a clear estimate before starting work. Ask if they are licensed, insured, and EPA-certified to handle refrigerant.
Also ask about warranty coverage on parts and labor, and whether a permit is needed for the repair. In some Phoenix-area jurisdictions, a permit may be required for certain AC work. A trustworthy contractor will be upfront about all costs and requirements.
- Are you licensed, insured, and EPA-certified?
- What is your diagnostic fee and what does it include?
- Will you provide a written estimate before starting repairs?
- Is a permit required for this repair in my area?
- What warranties do you offer on parts and labor?
Take this with you
Evidence and scope checklist
- Diagnostic charge and what it covers
- Evidence of the fault (photos, error codes, sounds)
- Part replacement and compatibility with your unit
- Refrigerant type and leak detection method
- Electrical component testing and safety
- Drain line or water damage inspection
- Labor rate and estimated time
- Permit requirements for your jurisdiction
- Warranty on parts and labor
- Post-repair commissioning and documentation
Common questions
What homeowners ask next
Can I fix an AC that's running but not cooling myself?
You can check the thermostat, air filter, and look for ice, but you should not open panels or handle refrigerant. Most causes require a licensed professional.
Why is my AC running but not cooling in Phoenix heat?
High outdoor temperatures can strain the system, but common causes include a dirty filter, frozen coil, refrigerant leak, or electrical issue. A pro can diagnose it safely.
Should I turn off my AC if it's not cooling?
If you see ice on the unit or hear strange noises, turn it off to prevent damage. Otherwise, you can leave it on while waiting for a technician, but monitor for safety.
Evidence
Sources used for this guide
Research checked July 31, 2026
- Homeowner HVAC and refrigerant FAQsU.S. Environmental Protection Agency
Refrigerant and technician requirements; no homeowner refrigerant work.
- Purchasing and repairing home air conditioners and heat pumpsU.S. Environmental Protection Agency
Repair/replacement and refrigerant context.
- Heating and cooling maintenance checklistENERGY STAR
Maintenance context and professional service boundaries.
Optional next step
Need an on-site professional?
Use the guide and worksheet first so you can describe the situation and compare the full scope. A referral is optional; you can also contact a licensed local provider directly.
We have not enabled a provider route for this site. Use the checklist to contact and verify local providers yourself; urgent hazards should go to the appropriate emergency or public service.