N6X/8X Models do have a limited 'defrost mode'.......all heat sources are shut off for 1-2 hours every 40-54 hours of operation (length of defrost and when it occurs depends on software in microprocessor in upper panel)
Temp in food compartment should not go above 44*F
DO you get a 'fault code'.........temp setting Flashing?
Do you know about the 'Diagnostic Mode' and how to access it?
See pg 63 of linked manual......screen 4 & 5 show stored 'fault codes' which may get a better idea of what is going on.
http://rvrefrigeratorrepair.com/wp-c...vice-N61x-N81x