98 envoy ac

my 1998 envoy with computer climate control is only blowing out boiling hot air no matter what i select. i have already had the blend door actuator and blend door replaced with no luck. blows out of vents boiling hot even when cold out and selector is on cold only time it has done diffrent is once when i swithced it to defrost it blew cool air out of the vents for a few seconds but then i heard a door closing and hot air startred coming out there too what could be causing this?? please help thanks jim

This is actually the wrong forum, this is for the 2002 up Envoys. The Jimmy forum is the right one. Anyway this is a control problem with the temp control/programmer components. There is a trouble tree test procedure in the factory shop manual or a subscription to Alldata.com