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.
HVAC Air Flow Switching to Defrost When Accelerating on Dodge Dakota
Average mileage: 162,625 (100,000–280,000)
21 people reported this problem
During acceleration, the HVAC switches from max cool to defroster mode. Not found source of problem.
1999 Dodge Dakota 201,000 mi, Visitor
Same here, AC blows fine at idle, once accelerating, goes to defrost.
1999 Dodge Dakota 120,000 mi, Visitor
No solution yet. Switches to defrost vents under acceleration. Suspected vacuum issue.
Same here,no vaccuum leaks and all the check valves under the hood check fine.
air flow switches from bilevel to defrost when accelerating
1990 Dodge Dakota 148,000 mi, Visitor
Air flow in vehicle keeps cycling and flips some sort of gate in the heater duct system.....plus in driving gear timing seems horrible...In park or nuetral it sounds decent but still using an incredible amount of gas.