HVAC Air Flow Switching to Defrost When Accelerating on Dodge Ram Wagon B250

The AC/heater (HVAC) system may unexpectedly switch to the defrost mode when accelerating. This system is operated by engine vacuum and should be inspected for any vacuum leaks if this problem develops.  There is also a revised vacuum check valve available to address this concern.

RepairPal Verified
Average mileage: 160,000 (160,000–160,000)
5 model years affected: 1990, 1991, 1992, 1993, more1994
6 people reported this problem
1 person shared problem details
over 50% of the time when accelerating
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