Hello all. I'm driving a 2013 Express 1500 cargo van for my business. The climate control vent settings is vacuum operated. It seems that there is an issue with either a lack of vacuum at certain throttle input or the climate control module is bad. When trying to maintain speed while driving up a slight incline without downshifting, the climate control will fade away from the front vent setting and air then comes out from both the defrost vents and floor. Once I back off the throttle the air flow returns to the front vents. Has anyone experienced this issue and knows the fix? I'm hoping it is a module problem but sounds like there could be a vacuum leak somewhere. TIA

 

that's usually a failed vacuum check-valve. Look for a T-fitting near the passenger front wheel housing.

 

I had no idea this was a thing. Just found a video about it. You are awesome! Thanks!

 

No problem. It will be near a black, plastic, grapefruit size sphere (the vacuum tank/reservoir)

 

I found that all of the vacuum tubing from the intake manifold to the check valve, to the vacuum tank was all deteriorated and collapsed. About $6 worth of vacuum tubing later, it is working properly again. Thanks again!

 

yep. An all too common story. The engine heat makes the thin plastic brittle, and vibration makes it fall apart. I think there is better stuff you can buy that is more durable. Just looks like thick rubber I think.

 

My engine was replaced under powertrain warranty. The existing tubing from the engine was some kind of thin rubber tubing which was all deteriorated. I'm not sure if that was what was there from the factory. The tubing running to the inside of the cab from the check valve is plastic. The replacement tubing from the parts store was a much thicker rubber tube.