hey guys, i just signed up, i have scrolled through this sites threads numerous times and this site is filled with knowledge. I just recently came across an issue that I think I know what it is but its a big job and want some other input if you guys have had similar issues.

vehicle:2002 sport trac
issue: ice cold air, but no heat, when dial is turned to heat it still blows cold air.

what i have done: took it to a shop for a diagnosis, both said it was and issue with the blend door and or the heater core. long story short this was not the issue. i put the dash back together and now i am thinking that it is the head gasket...wondering if anyone has anything else to try first before i take on that job.