Air Flap/Vacuum/Climate Control

[Kerry Griffith]

Thanks to David Head, Eric Kissell, Kneale Brownson, Dan Wing and others,
I've discovered and removed the large piece of folded cardboard that was
holding the recirculation flap open. It looks suspiciously intentional- the
red plastic vacuum line was certainly blocked intentionally! There are three
plastic vacuum lines; one white, one black, and one red. The red one had a
short length of flexible hose attached with a screw in the end. It appears
that said red hose should attach to a black rubber line that disappears into
the box surrounding the recirculation flap. When I remove the plug and
attached red plastic line to flexible black hose, all the air is sent
through the defroster vents. Putting said hoses back to their jury-rigged
states results in more normal heat/ventilation.
I'm fairly certain that this "fix" was part of an attempt to cure a
vacuum-related problem in summer that causes cold a/c air to be diverted to
the defroster ducts under boost. My question is: what problem does this
blocking of the red vacuum line indicate? Vacuum check valve? Vacuum motor?
AC controller?  
TIA. This list is great- my mechanics usually aren't monkey lads, but . . .

Best Regards,
Kerry