So the little vacuum servo that operates the 'fresh air' (re-circulation) flap on my 90 has officially crapped out (it's a manual HVAC box). I tested it with a hand-pump and it can't hold pressure, the electrical signal is being sent though. Because of this my cabin temp is getting excessively hot as it remains open to turbo-charged heat. Has anyone figured out a trick to replace this little thing without pulling the entire HVAC box? At the very least I'd like to keep the door shut as an interim solution.