Weak run capacitor causes poor cooling and compressor noise

Capacitor before repair

15.4 µF on a 30 µF section

Replacement capacitor

35 µF as required for the circuit

Compressor current after repair

4.70 A / 11.2 A nameplate reference

Condenser fan current

0.54 A / 0.77 A reference

Suction / liquid pressure

143 / 302 psig

Supply / return air

58°F / 77°F

Temperature split

19°F

1. 1Verified the cooling complaint at the supply air
2. 2Listened to the compressor and checked the run capacitor
3. 3Measured the capacitor far below its labeled value
4. 4Installed the correct replacement capacitor and restarted the system
5. 5Recorded current, pressures, and air temperatures after the repair

A severely weakened run capacitor was preventing normal compressor operation and cooling performance.

Replaced the failed run capacitor and verified normal operation with post-repair electrical, refrigerant, and air-temperature readings.

Final operating readings

A capacitor can be the primary failure even when the compressor still attempts to run. Verify the required capacitance from the unit data or wiring information rather than copying a mismatched replacement.

• Measure capacitance rather than judging by appearance
• Record compressor and fan current after replacing a run capacitor
• Confirm the repair with air-side and refrigeration-side performance

• De-energize, verify absence of voltage, and discharge capacitors using an approved method
• Use the specified capacitance and an equal-or-higher appropriate voltage rating