12 year old Goodman heat pump.

Outside fans starts immediately but after ~10 min shuts off. No mechanical sounds, vibrations, etc. associated with the fan shutdown - just cuts out as if powered off. Have not checked voltage to fan after shutdown

After fan shutdown outside unit humms with water vapor production while the inside air handler continues to blow ari. The condenser fan won't restart unless system is shut off for ~30 min.

Blower motor replaced 4 years ago. Capacitor and defrost board replaced but did not correct problem.

Fan spins freely after shutdown.

Symptom seems to occur at temps of 50 degrees F and below.

Thanks in advance

 

Id check if it is or not . That will tell you fan motor or other.

 

With heat pumps, the outdoor fan is expected to shut off during defrost cycles.

The fact that you indicate the unit hums suggests the compressor continues running (as it should during a defrost cycle).

Finally, the water vapor production could only happen when a heat pump has switched from heating to cooling modes (the hot gas moving through the condenser coils causes this water vapor, since the coil was at that very time likely somewhat frosted).

The three symptons you mention appear to indicate your heat pump is moving into defrost too often (10 minutes is way, way to often). The million dollar question is "why?"
Maybe a hanging defrost relay...maybe a defective defrost initiation sensor. Hard to tell without actually babysitting the unit to see what exactly is going on.

Do you have available the M/N of this unit?