Hey all.

Have a intresting issue with a EL GLI veichle.

When braking in traffic the HVAC system will switch from Recirc Air to Fresh if you have it in Recirc Mode.
Also when cruzing up a hill airflow is redirected to windscreen.

However. Overnight no vacume is lost from the system.
I have removed all vacume lines and checked for leaks and cant find any.
Also the one way valve PN D9AE-AA is operating correctly.
Has anyone seen this before. ?

Cheers

99% of the time it is the one way valve. How didyou test the system?

Applied vacume to the system manually and wated to see if the vacumme was lost.

As I said it will hold vacume for days if the car is not used.

Im thinking it may be to do with the intake manifold solonoid leaking air back in when under load.