Hi, I just started having a problem with my Atwood Hydro Flame Furnace (8500-IV). The furnace runs all the time no matter what setting I have the Thermostat at. Also, I tried disconnecting all the wires on the Thermostat and it still runs... Blower and Burner going full blast. Can anyone point me what to T-shoot first? Bad Thermostat? Bad Relay? ???