Another HVAC vacuum issue
 

Really getting tires of all these issues that this jeep has. The new problem: HVAC only works on defrost. Issue is known and been posted about a million times, but I am trying to see if with your help I can pin point the cause without throwing parts at the truck.

Everything worked fine yesterday and today the heat only blows from the defrost. When I flip the switch to anything else there is no noise, no hissing no nothing. 4wd engages fine so that part of vacuum works.

So my question: is it most likely a bad line? Bad vacuum ball or maybe bad check valve?

If the vac ball is bad controls should still work, right? The ball is there just to keep the vacuum when the car accelerating, correct?

Anybody?

You need the vaccum ball installed anc correctly working (no cracks/leaks) to be working. If I was to take mine out, it would only come out the defrost just as you say.

If your vaccum ball is fine and not cracked, check the lines for leaks (they all run off the intake manifold). You can spray ether across the lines to detect leak. It will bog down when you spray the ether and it finds a leak.

check vacuum line coming from manifold pressure to the vacuum ball. this was my problem, the hot engine melted the rubber when it wend around the engine.

thanks for the comments guys. Fixed it. It was a giant piece of ice totally engulfing the vac ball and blocking the lines. Took me an hour to deice it.