Hi, folks,

I've post the problem before about the defroster on my car. Here is some new input. I just found if I close all the other vents, and press Defrost button, the air will flow out strongly from the vent close to windshild. If I open one of the others, the flow will get weak. If I open the others all, there is almost no air flow at all. So, I suspect the defrost button can't switch the normal air flow to defrost air flow. Any one experienced the problem before? How to fix it?

Thanks!

Shawn
--
90' 240 DL wagon 138k

Behind the glove compartment is a vacuum diaphragm that is supposed to close off the dash vents when you push the defrost button. I moved up north for two years a couple of years ago and found that my diaphragm wasn't operating like it should. It was acting like yours, so because getting the frost off the windshield was imperative I used some bread ties to hold the diaphragm in the defrost position. I hadn't thought about that for a couple of years now as I've moved back to the southeast and don't need the defroster much anymore. The glovebox comes out easy and within a little while of pushing the defroster button you should see the diaphragm trying to work. (Naturally the engine has to be running to pull vacuum while you test).