My Heil H E 5000 heat pump is about 12-14 yrs old have had no problems but this year have noticed that the outside unit seems to be frozen up. The outside temp is in the mid forties and the unit seems to run and heat all right except that when checked the out side fan is not turning and the lower half of the unit is covered in frost and ice, could this be a sign of trouble. When I say no troubles I mean that there has been nothing significant enough to call a technician, but, there has been a noise when the unit is in heating mode, as it shuts down, that sounds like a buzzing inside the "a" coil, that dissipates after a short time. Please advise.
Thanks for your help!

With most heat pumps the outdoor fan runs unless the system is in it's defrost mode. When defrost terminates you should hear a "swoosh" noise & the fan should restart.

I have a heil 5 ton roof unit and a few days ago we had 3 to 4 inches of rain that lasted 2 days and caused rain to get into my unit and come through my ceiling and do damage to my house, it looks like it blew in my unit, kind of in the middle and ran down into my attic and into my insulation and eventually the ceiling sheetrock. You can see through separation on the unit where rain can blow into it, shouldn't there be a seal or gasket or et c...

Unless there is a damaged or unsecured acess panel, no water should be able to get into the unit. If the ducts are not sealed to the unit, you certainly could get water. If this ia a 5000 series, they haven't been made in probably 20 years or more.