Questions and Answers

Chevy Monte Carlo A/C Question Q. I have a 1998 Chevy Monte Carlo and I noticed that when I have the air conditioning on and the car transmission in "drive", the air flow moves from the facial dashboard vents to the windshield defrost vents upon acceleration. When I take my foot off the accelerator and coast, the air flow moves back to the facial vents. This problem does not occur in park or neutral when the accelerator is pushed, only when driving.

I'm told it's a vacuum based problem/issue. I am also told it can be either inside the dashboard or something under the hood. The engine runs smooth and there are no "hisses" or air leaks to be heard from under the hood. Any recommendations and specific parts to consider looking at for this DIY?

A. I would bet the house that it's a vacuum supply problem and it's probably under the hood somewhere. Look under the hood near the throttle body and trace the vacuum hoses from it to their destinations. One will run to the firewall and will be rotted or have a cracked check valve. You can't hear it hiss because it's a very small line.