I posted a couple of days ago about my HVAC stuck in default mode(The air always blowing out the defrost vents). I followed JMC's advice and started tracing vacuum lines starting at the controls. I definitely do not have vacuum anywhere under there. I can't hear any leaks and have replaced questionable areas of concern with new vacuum line in the engine compartment. I traced what vacuum lines I could behind the dash but they disappear behind the HVAC contol box. My question is where does this vacuum line that controls all of this come through the firewall. I know that my problem is vacuum related and I'm pretty sure that it's in the engine compartment. I just need some direction on where to start tracing it once it comes through the firewall.

 

Look behind the battery...there they are

 

Thanks for the help folks. The problem was that my vacuum line that feeds all of the HVAC had come unplugged from the firewall. I guess this happened when I was replacing the #4 coil and I had to remove all of the electrical stuff from the firewall to get back in there.