hvac unit

[killergmctruck88]

my havac unit works when it wants too so i tryed this hvac unit i got out of 94 in my truck and it makes the fan sound really odd.. is this normal or what? am i hurting anything

[killergmctruck88]

ok now i tried a unit from a 1992.. everything works like it should but there is a recir button, when i press it it sounds like it starts to suck air in from under the dash or something is that normal and am i hurting anything buy using that? and i also noticed when i goto window defrost the icons like the defrost icon and the lvl bar on the screen start to blink, is that normal??

[killergmctruck88]

ok so i been using the hvac control unit thats from a 92 and its been working fine but why does the C to H bar on the display start to blink after its been on for more then a few min and it wont let me go from hot to cold when it does that and when i use the defrost the defrost icon starts to flash? something wrong?