Day & Night
Failed Compressor Start Circuit / Run Capacitor
Outdoor fan runs but compressor does not; loud humming from outdoor unit
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Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
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Possible Causes
Failed compressor run capacitor, Loose compressor wiring at contactor or capacitor, Locked rotor compressor, Failed hard-start kit (if equipped)
How to Fix / Troubleshooting
Safety first: Turn OFF power at the disconnect. Capacitors can store charge; discharge safely before handling.
- Step 1 – Inspect capacitor: Locate the dual run capacitor. If bulged, rusted, or leaking oil, replace it with the same capacitance and voltage rating.
- Step 2 – Check wiring: Verify compressor wires are firmly attached to the HERM terminal on the capacitor and to the contactor.
- Step 3 – Listen after replacement: Restore power and call for cooling. If the compressor still only hums briefly then trips, it may be locked or failing.
- Professional service: A technician can test compressor windings and install a hard-start kit or replace the compressor if necessary.
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Repair Difficulty
Hard
4/5
Required Part
Dual Run Capacitor
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