Unit runs fine for 3-7 days, then screen on digital thermostat goes blank and unit shuts off for about another 5 days,then all of sudden unit runs fine,problem not batteries for thermostat! When unit stops there's no power to thermostat, sounds like control board problem,have anyone heard of this problem before,how can I troubleshoot control board? please advise, now unit won't start ,been off for about a week, a/c started 2 weeks ago ,ran fine for for 3 days , shut off and has'nt started since.