Originally Posted by
mrobertweiss
there is an actuator for cabin air door right above and to left of the grey vacuum reservoir youve disconnected. That actuator , if it leaks will make the noise. Its about two inches high and an inch wide, oval shaped and is unlabelled in the parts manual but is drawn in. it operates a spring in the cabin air box that its attached to. The part is unobtainium. I managed to get a new one but havent tackled getting it in. Theres a steel bar in front, and removing the whole dash doesnt look like itll improve access. Its hard to localize the noise, its high pirched and your ear doesnt easily have directional capability with it. its like a dog whistle. You can stop it by putting the control swithch to the dot just above the zero on the AC/htr head unit. Then no fresh air, and it will also whistle probably while the ac and or heat is actuated from 1-5. Pain in ***.
Hi Robert, if the actuator is for the air recirculation flap it’s activated by vacuum pressure from the grey reservoir box that you mentioned behind the dashboard, mine is a right hand drive car so this box is behind the glovebox on the left side of the dashboard and I can see it by removing the trim panel under the dash and shining a torch up behind the glovebox itself. You can disconnect the vacuum supply to this reservoir by blanking off the grey pipe from the engine, it runs under the battery tray and through a rubber grommet into the interior of the car. I tried this on mine to eliminate it from my inquiries, but the noise didn’t stop, the heater and air con still works but the recirculation switch doesn’t, this doesn’t bother me so I’ve left it like that and I will switch the fan off if I want to stop the outside air coming into the car, my early cars didn’t have a recirculation feature and I find that using it steams the windows up after a few minutes anyway. I hope you get yours fixed and if you don’t fancy dismantling your dashboard you could blank off the grey pipe like I did. I made a post about this noise recently, it’s entitled central locking vacuum valve box. Best wishes!