My 2007 Prius with 90,000 mi makes a squeaking noise when switching from outside air on the ventilation system to re-circulation and back. I have an extended warranty and asked the dealer to look into it on my last car maintenance check-up. They told me it would be $110 just to look, and that it could be a belt which would be regular maintenance. Help!
Why does ventilation system make a noise? on 2007 Toyota Prius
Mine does it too (2007 - 150k miles). I think it is a fresh air vent closing when I switch out of recirculate or AC mode. I don't find it any more alarming than any of the other funny noises this car makes...