Dodge A/C - changes where air comes out while driving



I have a '96 Dodge Ram Van, B2500. When accelerating or driving uphill, air comes out of heat vent or defroster vent instead of dashboard outlets. When load is off engine, air comes out of dash again. Seems vacuum related, but dealer couldn’t get problem to repeat, and said engine vacuum is OK.


Sounds like a vacuum problem to me. It will take a bit of tracing to determine the problem as it could be under the hood or inside the dash.
Split or knocked off vacuum hose, cracked vacuum canister, defective one-way valve, dashboard mode control or vacuum pod, defective brake booster or cruise control servo, etc.

The easiest way to determine this, and it’s what I’ve always done, is connect a vacuum gauge to an intake manifold vacuum source.
The gauge will let you know instantly if there is a vacuum problem and which general area. I then go over the vacuum lines if there is a problem and pinch them off one at a time with an old pair of surgical forceps until there is a normal vacuum reading.

If the dealer did not test drive the vehicle down the road and use a vacuum gauge then they’re just blowing this problem off more than likely or they’re clueless on where to start.

I would suggest (if you can’t do this yourself) that you find a well established shop, preferably with ASE techs, and let them have a go at it. It may be nothing more than a loose or split hose, especially if you’ve had someone servicing it just before this happened.
Don’t know if any of this will help or not, but my humble optinion is that this may not be a serious problem.:slight_smile:


I have to say that your dealer is not being totally honest with you, since this has been a known problem with Chrysler products for about 20 years! However, I agree that the dealership probably have no way of correcting the problem if Chrysler’s own engineers apparently weren’t able to design an HVAC system without this tendency for a couple of decades.

A couple of weeks ago, Ray & Tom were talking about this same ongoing issue with Chrysler products when an owner of a fairly new Dodge pickup called up with this exact complaint, and all that they could suggest was to research whether there might be a TSB for correction of the problem. So, you might do the same thing–either search for a TSB on your own, or ask the service department to search for a TSB on this common Chrysler problem.

In the long run, you may have to chalk this up as a relatively minor problem that you will just have to live with.


It’s most likely the one-way vacuum valve, seen it a thousand times.