with ac/heater running
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2004 Dodge Ram 2500 Question: what causes the ac vents to change from floor to panel and back by themselves
Answer #1Mobile Tek May 13, 2014, 06:04Enthusiast
If vents are controlled by vacuum a loss of vacuum would cause servos to go to a rest position and usually air only comes out of floor and defrost vents. Diesel engines need a vacuum pump because they unlike a gas engine have no or very little vacuum.
Replyskyhawk11, May 13, 2014, 10:41Rookie
do you know if there is more than 1 vacuum check valve,in the system