Dodge Ram Van 1500 Problem Report

Dodge Ram Van 1500 HVAC Air Flow Switching to Defrost When Accelerating

(87 reports)

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.

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. -
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. -
heater/ac only works on defrost -
ac and heat only comes out on defrost. -
a/c switches to defrost on acceleration or moderate incline -
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 -
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. -
AC/heater awitches to defrost when acceralating -
I have the same problem on my 97 3.9L B1500 I installed two check valves this did the trick -
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 -
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! -
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. -
accelerate lose air cond -
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 -
same as above -
Ac went to the defrosters and and won't come back -
Have same problem with A/C Heater system will switch to defrost mode when engine is accelerated. I replaced two check valves in the HVAC system,did not solve problem. I live in a area where I drive has a lot of hills, so the system switches from normal to defrost mode quite often. This involves a 1999 Dodge Ram 1500 Truck with a 5.9 Liter Engine with automatic transmission.Need help to solve this problem. thank you. -
Know nothing about vehicles but, its as though there is a baffle connected to the switch on dash that switches the air from floor, vent or defrost or a combination of any of those, DOES NOT WORK!! The air only comes out the defrost area, A/C or heater. very frustrating in 100 degree weather!! -
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