HVAC Air Flow Switching to Defrost When Accelerating on Dodge Ram Van 2500

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: 126,062 (22,000–265,000)
9 model years affected: 1995, 1996, 1997, 1998, more1999, 2000, 2001, 2002, 2003
28 people reported this problem
Get Your Car Fixed at a RepairPal Certified Shop.
We certify shops based on expertise, quality work, and verified customer reviews
Viewing 1 - 12 of 12 problem details
When I accelerate the a/c switches to floor and then defrost mode. I have replaced the check vavle and have checked all my vaccum lines and have found no leaks, but the problem is still there. Any Ideas.
1999 Dodge Ram Van 2500 74,000 mi,
Daytona Dodge just wants to keep changing the front resister even after being told precisely what the problem is. Then just hands me the key, I start the van and NOTHING has changed except for the amount of $$ in my bank account. I told the owner about it and was treated like I was the liar when in fact they are the ones who passed it off to me as fixed. Was able to get $100 returned off bill and was asked to never come back to his dealership because I had initially said that whoever claimed to have fixed the problem must have lied. I'll make the 20 mile trip to New Smyrna Dodge for all my work from now on. Problem still exists as of 4/07/2013 and the fan speed only works in the high position. Any vacuum diagrams for this vehicle?
My air flow switching to defrost when i accelerating. Also i can not get any heat only cool air for heat i Replace the heat control and the themostate i am thinking it may be the vacuum help
2002 Dodge Ram Van 2500 22,000 mi,
When running either the heater or AC and go to accelerate, the airflow will switch from blowing out the front vents to the floor, or defroster vents with no consistency until up to normal speed or you take your foot off the gas. Even when at normal speed and it is blowing out the front vents and you even push on the gas a little it will switch again to the different vents...
2000 Dodge Ram Van 2500 53,000 mi,
HVAC Air Flow Switching to Defrost When Accelerating
2000 Dodge Ram Van 2500 109,000 mi,
Air or heater will switch to Defrost area during hard acceleration or load going uphill. Have not diagnosed or solved yet.
1997 Dodge Ram Van 2500 160,000 mi,
Back fire during start like a 3 pop, pop pop, then It seems to idle ok for a sec and then the lAg of and bucking and low horse power. Just changed water pump and radiator and over heats in weird and different times. Replaced thermostat also!! Fuel runs rich also please help. Oh yea the defrost to vent switch problem also exists
2000 Dodge Ram Van 2500 123,000 mi,
Same problem with 2000 DODGE Ram 1500 Laramie, no backfire problems and runs great {318 ci), just aggravates the ---- out of me. You can hear the flapper switch and drop back when acceleration stops and air resumes correctly. Haven't fixed yet, winter is almost here, hope heater is not affected by problem.
2002 Dodge Ram Van 2500 100,000 mi,
Bought it 6 months ago, since Dodge is famous for electrical problems I thought that was it, I will check for vac leaks.
1999 Dodge Ram Van 2500 80,000 mi,
AC air flow switches to defrost when accelerating or going up hill.
I have the same problem withair flowing to the floor and defrost would like any feed back Also need a/c parts. also a/c dryer a/c condensor a/c lines
1997 Dodge Ram Van 2500 265,000 mi,
Heater switches to defrost during acceleration