93 Jimmy Fan working no air coming through vents

so I have a 93 jimmy and all coolants etc have been topped up...i also noticed that ll my gauges work great and are all hovering around the mid point...also the fan is running the belt is fine and all that.....

question is: why isnt there air coming through the vents...no heat...vent.....defrost..nothing however the dash gets warm and the gauges are fine..

PLEASE HELP...

If you have plenty of hot air coming out of the defrost vent at the base of the windshield then your source of vacuum is suspect. If the fuel injection is a CPI (big sculpted runner intake manifold), the vacuum source is the fitting at the passenger side/rear of the intake manifold near the distributor....check to see if a vacuum line is connected there.

There is a vacuum-operated diaphragm that selects the mode (dash, floor, defrost, mix). When you move the dial/lever and all you hear is hissing, then you probably have a hole in the diaphragm and will have to replace it. Mine was ~$15 from the dealer.