Stretch wrote:

1) The reversing valve switches into cool mode. This makes a loud
whoosh!! sound. This makes the outdoor coil warm to melt ice or frost
on the outdoor coil...
2) The outdoor fan shuts off while the compressor keeps running. This
keeps the outdoor air from being cooled by the outdoor air while the
unit is defrosting.

Why do we need to keep outdoor air from cooling outdoor air? :-)

Why not turn off the compressor and leave the outdoor fan running, wasting
less energy, if the outdoor air is above freezing? We can melt about
1000(36-32)/144 = 28 lb/h of ice with 1000 cfm of 36 F air.

Or turn off the compressor and keep the fan running BEFORE ice forms...

Nick