I received info from a previous cnet post and contacted an Acadia owner who had the same problem. He reported that a year ago he found out via his HVAC installer that a new icing sensor board was being retrofitted and this fixed the problem.
I managed to make contact with the Tech rep at Hallowell (a Mr. Norm Springer) who verified that my system needed the same fix. (All units distributed through FW Webb which was later than my install had been upgraded)
The part is on its way to my HVAC company - and I am hopefull that it will fix the problem. Thank you cnet.
I am experiencing severe icing problems with my 2 year old acadia when humidity is high and temp is about 40. I can't seem to get response from factory and service people were not helpful. I turned unit off and deiced to recover - but need to leave for the winter soon and am terrified I bought a product that has a significant and perhaps fatal flaw. I am suspicious about lack of posts on this subject on the net since local service man had heard "rumors" of Hallowell problems - and had icing problems on one of units they installed.