Here is some background on my heat pump.

This is the second winter since this unit was installed. The first winter every thing was fine and quite as can be. This past summer we had a lightning strike which fried the defrost control board. It was replaced and now when the unit goes through defrost mode i makes a loud vibration noise from the outside unit to the attic unit. Loud enough to wake you from your sleep! My HVAC guy says this is normal but it was not noticible at all last winter.

Any ideas or suggestions.

Thanks,

Jay

You may have some non condensibles in your refrigeration system. Which means that the freon would have to removed, the system vacuumed, filtered and the freon replaced.

I've also seen vibration when the high pressure line snubber was removed or relocated during service.

Glad to see you helping people here, Steve. Your web site at http://www.callallied.com/wwwboard/wwwboard.html
has really become helpful since the WWF of HVAC has changed policy toward helpfulness.