Vacuum value will change depending upon engine load.

When testing pods at the switchover valve it's simpler than that. Basically if when connecting the aux vac source to the removed hose, if it holds a vacuum it's good, if not it's bad.

With the exception of the defrost vent, which is POSSIBLE with lots of new swear words to replace without remving the dash, replace ALL pods if even one of them is bad. After you finish with this 15 hour job, it will be clear why you replaced them all.

Best of luck with it.

__________________
2001 SLK 320 six speed manual
2014 Porsche Cayenne six speed manual

Annoy a Liberal, Read the Constitution