The Ruud outdoor unit fan runs but the compressor does not; the unit hums briefly then clicks off, resulting in no cooling.

Safety first: Turn off power at the disconnect. Compressor circuits carry high current; improper work can be dangerous.

• Step 1 – Check the capacitor and hard-start kit: Many Ruud units use a dual run capacitor and sometimes a separate start capacitor with a relay. Inspect and test these components; replace them if they are out of specification.
• Step 2 – Listen for overload reset: If the compressor overheats, its internal overload will open. Allow the unit to cool for 1–2 hours with the power off, then retry.
• Step 3 – Technician testing: A technician can measure locked rotor amps (LRA) and perform a megohm test on the compressor windings to determine if the compressor is shorted or grounded.
• Step 4 – Compressor replacement: If the compressor is locked or electrically failed, it must be replaced by a licensed HVAC technician, including refrigerant recovery and system evacuation.