[akader]

All of the mixture vents in the dash are controlled by vacuum. The some of the small vacuum hoses along the firewall near the battery are the control hoses for the vents under the dash. These hoses and hard plastic connectors will deteriorate with age and battery acid so close. My suggestion is to check these for leaks/breaks and repair if so. This is identical to what happened on my 98 Exp and cured the problem.