Wondering if this has happened to anyone with digital HVAC controls. AC works but only blows through defroster. Will not switch. I saw the post about vacuum lines but I do not see any vacuum lines on the back of the digital Control module.

 

You should fill out your profile with your basic car specs; it makes it easier for us to help when we have some basic info to work off.

It seems as if your car has a Digital cockpit so your HVAC will be electronically controlled and not vacuum controlled. While there is still vacuum needed,...... this limited vacuum connection occurs at the MODE Control Solenoid and not at the digital HVAC controller. If your car is a Digital Dash Trans AM than this is what controls the blower air flow delivery "MODE Solenoid looks like; it can be found under/behind the dash housing on the passenger side.

 

exactly right on specs. So if I find that the vacuum is good to the module then I probably need a new module

 

That would be a 'best guesstimate' based on very simple observation / investigation. IMO: No electrical diagnosis should ever be concluded without a voltmeter in hand to confirm/rule out assumptions. It's possible - not likely but possible - that the Module might is working fine but a big pile of acorns is jammed inside the heater core box and not allowing the internal flaps to operate properly; maybe the wiring or plug @ the Module is bad,...... Just saying that an educated guess isn't always a home run.