Why is my AC running but not cooling?
An AC that runs without cooling is most often a dirty filter choking airflow, a failed capacitor, or low refrigerant from a leak. The filter you can fix in two minutes; a frozen coil means shut it off and let it thaw before a tech comes, or the real problem can't be diagnosed.
Likely causes
- Clogged filter — Starved airflow freezes the coil and kills cooling — check this first, always.
- Failed capacitor — The outdoor fan or compressor won't start properly; a common, relatively cheap repair.
- Refrigerant leak — Ice on the refrigerant lines plus weak cooling. Refilling without fixing the leak buys weeks, not years.
- Dirty outdoor condenser — Cottonwood, grass, and debris insulate the coil so heat can't escape.
What you can check yourself
- Replace the filter. If the indoor coil is iced, turn the system off (fan on) for 3–4 hours to thaw.
- Clear debris from around the outdoor unit — 2 feet of clearance on all sides.
- Check that the thermostat is on 'cool' and below room temperature (it happens more than anyone admits).
Typical cost
Typical repairs in Denver, CO: capacitor $150–$350; refrigerant leak repair + refill $450–$1,200; fan motor $300–$600.
When to call a pro
Ice keeps returning, the breaker trips, or it blows warm after a filter change and thaw — those need a tech, and running it meanwhile can kill the compressor.
HVAC pros in Denver, CO
- Motili · 1900 Wazee St #1533, Denver, CO · +18006699656
- US HVAC Home Service Denver · 1881 Curtis St #2C, Denver, CO · (719) 399-1053
- Pro HVAC Denver · 600 17th St, Denver, CO · +18003036170
- Aether Mechanical · 1630 Welton St, Denver, CO · +13034147770
- Med Air Pro · 290 Park Ave W #118, Denver, CO · (720) 369-7063
- Thermiq Services, Llc · 2590 Welton St Ste 200 Pmb 1010, Denver, CO · 13032183388
- Zero Homes · 3120 Blake St, Denver, CO · +13038488606
- Mile High Air Duct · 3200 W Colfax Ave, Denver, CO · +17204697519
Get free quotes from Denver, CO pros →
Data by Servik — verified local pros from official license records and public sources. Cost figures are typical ranges, not quotes; a pro's written estimate is the real number.