The dash in my 2006 Prius was squeaking for a long time. Today I decided to fix it. I went to the local hardware store and bought several adhesive rubber bumpers. I peeled off the adhesive backing and carefully wedged the bumpers in the dash. Two rubber bumpers were needed. I drove the car and the squeak was gone. I have enclosed a photo showing where I placed the bumpers. The photo shows a sample of the bumper I used in the center.
I have been driving along and heard a squeak and pushed on that piece of plastic and it stopped. Great (and cheap) solution! Thanks.
Thin adhesive backed foam is good for this too, like the thinnest weather stripping you can find, or felt tabs even. - D
Here's a picture of some foam I applied to the underside of that vent piece. It helped somewhat. Marvinh
