Just sharing.
I have 5 tom TRANE heat pump.
Over a month ago, outside blower fan stopped working. Compressor worked fine, fan stopped.
Fortunately, I have very nice HVAC guy who told me to look at condenser in outside unit control pane.
Turned out ot be, it swell and quit its electric function.
I found one locally next day for $12 plus tax et voila.
Also bought a spare one, just in case.
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

So, if you have same issue - comp works (noticeable buzz) but fan does not turns on, start with condenser. Just really pay attention to how it's connected. Mine had 4 wires and, as you can tell, condenser has way too many prongs.
One that went bad had bottom and top rounded out. You can remove it, set on something hard and flat, like countertop, and if it rocks side to side, it's bad. New one sits flush and flat.

 

Your talking about a defective capacitor.
If you were to read thru A/C threads you would see over half of them had capacitor failure issues.

 

Yes, capacitor. Just came here to correct this, but thank you for quick fix.