What usually fails
Most AC repair calls come down to a short list of parts. A run capacitor is a small metal cylinder in the outside unit that gives the compressor and fan motor the jolt they need to start. Summer heat wears capacitors out, and a failed one is behind a large share of calls about an outside unit that hums but will not spin. The part costs under $50, and the repair usually runs $150 to $400 with the visit.
After capacitors, the usual calls are a clogged condensate drain, low refrigerant from a leak, a burned contactor and a dirty indoor coil that ices over. Pine pollen in April coats outdoor coils in yellow dust across Chapel Hill, and a coil that nobody rinsed runs hotter all summer.
Signs you need a repair
- Air from the vents is room temperature or warm while the system runs
- The outside unit hums, clicks or buzzes but the fan does not turn
- Ice on the large copper line at the outside unit or on the indoor coil
- Water in the drain pan, on the floor, or dripping from a ceiling under an attic unit
- The breaker for the AC trips more than once
- The house will not get below 78 in the afternoon with the thermostat set at 72
What to check before you call
Look at the thermostat first. It should be set to Cool with a set point below the room temperature. A dead battery blanks the screen on many models. Then check the breaker panel for a tripped AC or air handler breaker and reset it once. If it trips again, leave it off and call, because a repeat trip points to a shorted motor or compressor.
A clogged filter will not stop the system outright, but it can freeze the indoor coil within a day. If the filter is gray and caked, replace it and set the system to Fan only for two hours to melt the ice before running Cool again.
Typical costs
| Repair | Typical price |
|---|---|
| Diagnostic visit | $89 to $150 |
| Capacitor replacement | $150 to $400 |
| Contactor replacement | $150 to $350 |
| Condensate drain clearing | $100 to $250 |
| Outdoor fan motor | $350 to $900 |
| Refrigerant leak search and recharge | $400 to $1,500 |
| Compressor replacement | $1,800 to $3,500 |
If the system is more than 12 years old and needs a compressor or a coil, ask the tech to price a replacement next to the repair. On a 15-year-old unit, a $2,500 compressor repair goes into equipment that will likely need replacing within a few years.
Questions
How long does an AC repair take?
Capacitors, contactors and drain clearing are usually done in under an hour once the tech is at the house. A refrigerant leak repair or a motor that has to be ordered can take a second visit.
Why is my AC running but not cooling?
Usually the compressor has stopped because of a failed capacitor, or the system is low on refrigerant from a leak. A frozen indoor coil from a dirty filter or a weak blower causes the same symptom.
Is it safe to keep running an AC that is not cooling?
Turn it off if you see ice or hear grinding. Running a frozen or low-refrigerant system can burn out the compressor, which turns a $300 repair into a $3,000 one.