OK, I did some testing tonight. I think this confirms it is the auto defrost setting: (ambient 40F)
setting on and plugged in set to fan only - draws +3KW
setting off and plugged in set to fan only - draws -3 KW (the 240v 16a charge rate)
The DIC displaying fan-only is misleading, it should display "fan-only auto defrost on". All this time I was lead to believe no significant power was being used when fan-only was displayed.
Also, checked the rear defrost, when turned on there is no change on the DIC , so I assume its using the 12V battery.
Thanks for the help!