98 ram 1500. 5.2L. My air/heat only blows from the defrost vents. I checked the outside vaccum hose that comes through the firewall and its good. My Dash is cracked pretty bad, so I ordered a dash mat to cover it. So I will probably chip away at the dash to be able to see the inside where the vacuum line comes through. Is there anything specific I should look for to fix the problem inside the dash?