On my 07 Beaver PT, when i turn on my Alladin Monitor to show Coach Electrical Status,  it sometimes give a message " AC Input Open Ground" for about 2 seconds then indicates "Shore Power Connected".    Also it always indicates that line one is  118 V. and line two is 120 V.  I have checked all the 110 v outlets in the coach and do not find any indication of "open ground".   Any Suggestions?