Heater Controls Losing Vacum

[shadowsleeper]

i have a 89 shadow 2.5 TI 5 sp.
i've tried a couple check valves under the hood, but nothing seems to help
when pulling a hill or getting into boost, the A/C starts blowing out the defrost vents
i'm changing the heater core at this time,not much heat in the winter
is there something i should be looking for?
vacum lines or leak, more check valves?

[rbryant]

I think there is also a check valve under the dash.

-Rich

[minigts]

Rich is correct. There is one for either the red or brown vacuum line. Again, something ELSE I have removed from my car, so all I could provide would be the diagrams. Let me look to see where that file is though.