2000 Grand cherokee heater doesn't Work

I have a late 2000 Grand Cherokee that only blows cold . It has a digital readout and two heat controls , one for driver and one for passenger.
I can't find a repair manuel that has this configuration of heating. The digital readout works and the heat controls both do not have a stop on them and have a continuous turning . What may or might be the problem?

Not sure, vacuum leak perhaps?

You'll probably have better luck on the Grand Cherokee forum; moving your post there for you.

I think you'll find your answer here.
http://www.wjjeeps.com/climate.htm