Hi all; I have a 2002 Ram Van 1500 with the 5.2 litre engine. It has 56,000 kilometres on the vehicle. When I accelerate, the heating system defaults to defrost. When I let off the throttle, it comes back to whatever setting it's on (usually vent or heat/footwells). This has got to be a vacuum issue, I would think. I've checked vacuum hoses, though, and all seems to be well. Has anyone else experienced this or can anyone offer any guidance as to where I should look? Thanks; Tim

 

If you're positive there's no vacuum leak, then inspect the HVAC check valve. It located on the passenger side of the intake. The valve should only allow air to blow through in one direction, so if you can blow through it both ways then that's the problem.

 

Why on earth did dodge stick with vacuum controls in the HVAC system for so long?

 

Most vehicles over the past 25 years have vacuum controls in them, not just Dodge.

 

Then I should rephrase... why is it that there is so much trouble with Dodge (vans in particular)... I've been driving vans for about 13 years now and I've not yet driven a dodge van where I haven't encountered this particular vacuum issue. In fact, I think that the '93 ford van I had was the only one that didn't have this problem. Dodge and GM seem to be the worst with this.

 

See, then it isn't just Dodge.

BTW, Ford Expeditions and F series trucks have major vacuum hose issues.