why does the a/c stop blowing thru the front vents and comming thru tha defrost vents

Asked by Jul 21, 2013 at 05:45 PM about the 2001 Dodge Ram 1500 4 Dr SLT 4WD Quad Cab SB

Question type: Maintenance & Repair

When I accelerate wwith the air on it stops blowing thru thefront vents and sterat blowing
thru the defrost and when you let off the accelerator the the air starts blowing thru the
front vents like it should.  Please help. Thanks.

4 Answers


Could be a vacuum issue. Some air diverters in the duct work are vacuum controlled. Not sure if yours is but if it is that's where I would look first.

4 of 4 people found this helpful.

Yes vacuum is supplied to the air control assembly by tubing to the intake manifold. Inspect the vacuum line for leaks and cracks. There is also a check valve in that line. (Note direction of check valve before removing it for testing) Apply 8 inches of vacuum, with hand-held vacuum pump, to engine side of check valve. You should be able to pull air thru the valve. Apply vacuum to air control side of check valve. The valve should hold vacuum. If not replace the check valve.

2 of 2 people found this helpful.

Check valve is connected to intake manifold with black vacuum supply line.

3 of 3 people found this helpful.

I have a 1997 Ram 1500 and dandyoun is 100% correct. My face vents would blow until about 1/3 throttle and then they would shut off until I backed off of the gas pedal. My check valve was located on the passenger side with a 90° elbow that connected it to the intake manifold just to the rear of the pcv hose nipple. I could blow air through it in both directions so I cleaned it with Brakeclean and it is working perfectly again. Problem solved. Thanks dandyoun!

1 of 1 people found this helpful.

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