Originally Posted by wa8yxm
Since on MOST automotive (Including Evans) HEVAC systems DEFROST is DEFAULT I have only 2 suggestions.
I forgot all about, defrost being the default , when I posted, that will narrow the possible causes.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
2000 Caravan toad, Remco & Blue Ox.