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 Ram Van 1500
Average mileage: 128,519 (50,000–272,000)
93 people reported this problem
40 people shared problem details
1997 Dodge Ram Van 1500200,000Visitor
A/C blows normal until you accelerate then it moves to the defrost vents then the feet vents. when I lift off the gas it imediatly returns to normal.
1999 Dodge Ram Van 1500135,765Visitor
my problem is that it stays on defrost wont change to heat or vents. does antbody have a solution
We travel on the highway as we increase speed the ac/heater switches over to defrost ....we release the gas pedal it switches back to normal any solutions.
1997 Dodge Ram Van 1500174,000Visitor
heater/ac only works on defrost
1998 Dodge Ram Van 1500170,000Visitor
ac and heat only comes out on defrost.
2001 Dodge Ram Van 1500135,000Visitor
a/c switches to defrost on acceleration or moderate incline
1999 Dodge Ram Van 1500125,000Visitor
A/C blows normal until you accelerate then it moves to the defrost vents then the feet vents. when I lift off the gas it immediately returns to the floor.
I have a 1996 dodge ram 1500 with 3.9. when I accelerate the ac/heater switches from vent to defrost, I dont know how to fix or check for problems
1996 Dodge Ram Van 1500160,000Visitor
I have the same problem on my 97 3.9L B1500 I installed two check valves this did the trick
1998 Dodge Ram Van 150070,000Visitor
Ac changes to defrost when stepping on the gas
2000 Dodge Ram Van 150070,000Visitor
Heat or ac redirects to defrost when accelerating.
1995 Dodge Ram Van 1500158,000Visitor
the blower will switch from floor to defrost upon acceleration and back when coasting
2001 Dodge Ram Van 1500150,000Visitor
Not fixed yet
2000 Dodge Ram Van 1500143,000Visitor
When the van is accelerating the AC will turn redirect to somewhere else, maybe the defrost vents, and when I let off the gas the AC comes back
2001 Dodge Ram Van 1500110,000Visitor
switch for the air fan speed has when out two times you have to buy the hole switch control temp/fan speed/turn heat and air on / and mirrow defrose
Hoping to find out what to check to make the dash vent operate again... Thanks!
2001 Dodge Ram Van 1500272,000Visitor
When accelerating, especially when accelerating uphill, the air flow switches from my front dash vents to my defroster vents. The problem is a vacuum leak, I just don't know where. I have seen reports from other vehicles that the vacuum leak would be in the vacuum line to the exhaust manifold; specifically the valve there is either dirty or damaged and can't hold any pressure.
1999 Dodge Ram Van 150050,000Visitor
accelerate lose air cond
1999 Dodge Ram Van 150057,000Visitor
Air come out thru the vents ,at soon i step on the gas pedal it switches ,to defrost by itself ,i let go the gas pedal and it switches to the floor
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