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 Boston, MA: 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 Boston, MA
- Premier Mechanical · 220 Commercial St, Boston, MA · 6175809115
- Smart Click Energy · 175 Portland St Fl 4, Boston, MA · +16179734130
- Boston Heating & Air Conditioning · 276 Washington St #104, Boston, MA · 8008195184
- Colt Home Services · 110 Stuart St, Boston, MA · 6174463690
- Farina Corporation · 24 Spice St, Charlestown, MA · +16172420365
- Hunter & Sons AC & Cooling · 227 Cambridge St, Cambridge, MA · +13392205000
- Arlex Energy · 275 Massachusetts Ave, Boston, MA · +17818623400
- S Boston Plumbing Specialities · 15 Elkins St, Boston, MA · 6173159036
Get free quotes from Boston, MA 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.