heater help

my heater only seems to be blowing warm air and not blowing very hard,just enough to keep the window defrosted. when ur outside the jeep you can hear it blowing below the windshield seems weird never noticed that on my other xj's anyone know if that normal?

There is a mixing valve on the passenger side of the engine, follow the two hoses coming out of the fire wall to a small funny looking thing, it has a vac line going to it. They do go bad or you could have a vacum leak. See if the hoses are hot on both sides of the mixing valve.