98 xj air blows strong but when switched to full heat it blows weak

when i put it to full heat it sounds like it closes off the whole system and makes the blower sound like if you put your hand over the end of a vacuum. and the warm air barely comes out. my guess is the heater core has leaves or something on it, but i would just like some input before i rip the dash off.

Not the heater core. Heater core only provides the warmth from the engines coolant not the air flow.

Check the lower floor and upper windshield for air flow. The damper door maybe stuck. Not sure if the later years are electric or vacuum valve operated doors. The older jeeps use vacuum and a loose or leaking vacuum line can keep them from working right.

this post helped alot thanks