Carrier AC Repair: A Failed Capacitor and a Low Charge
The air conditioner was blowing cool air, but not cold, and the house took longer and longer to cool down. Our technician found two problems working together, a failed dual run capacitor and a refrigerant charge that did not account for the long line set, and fixed both in the same visit.
Cool air, but not cold, and cooling that came and went
The homeowner called because the air conditioner was producing some cool air, but not as cold as it should, and the system was taking longer than usual to cool the home. When our technician arrived in August 2026, the system was cooling on and off.
The equipment is a 5-ton Carrier central air conditioner installed in 2017, running on R-410A with a TXV at the indoor coil. The unit sits behind an iron fence along the side of the house, connected to the indoor coil by a long refrigerant line set.
What we found
The air filter was in acceptable condition, so it was not restricting airflow. Our technician checked the electrical components and connected gauges to read the refrigerant pressures. Two faults showed up.
A failed dual run capacitor
This one part helps start and run both the compressor and the condenser fan motor. When it fails, both motors struggle, which is a common cause of cooling that comes and goes.
A refrigerant charge that did not match the line set
The nameplate lists a subcooling target of 10°F. We measured 4.4°F, with high superheat, so the system was undercharged. A long line set needs more refrigerant than the factory charge provides, and this system was running short of it.
What Cold Cloud Mechanical completed
Both problems were fixed during the same visit, after the homeowner approved the written estimate.
- Checked the air filter, the electrical components and the refrigerant pressures.
- Replaced the failed dual run capacitor that serves the compressor and the condenser fan motor.
- Installed a hard start kit on the compressor to reduce the strain on every start.
- Added refrigerant and set the charge by subcooling, the method listed on the unit's nameplate for its TXV, until it matched the 10°F target.
- Ran a full operating test and confirmed the compressor and the condenser fan were working properly.
The result
After the repair, subcooling read 10.6°F against the 10°F target, and superheat came down from 32.5°F to 14.1°F. The system was running at the charge target on the nameplate. Charging by measurement, not by guesswork, is how we approach every repair.
Capacitor replaced
The compressor and the condenser fan now run on a new dual run capacitor.
Charge at the factory target
Subcooling went from 4.4°F to 10.6°F, matching the 10°F target on the nameplate.
Easier starts for the compressor
The hard start kit reduces the load on the compressor and the electrical parts each time the system turns on.
Is your AC cooling on and off?
We find the cause with measurements, explain what we found and fix it once you approve the estimate.
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