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.

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Average mileage: 160,000 (160,000–160,000)
5 model years affected: 1990, 1991, 1992, 1993, more1994
6 people reported this problem
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1992 Dodge Ram Wagon B250 160,000 mi,
over 50% of the time when accelerating