HVAC weak

My daughters' 1993 touring sedan has a perplexing problem with the HVAC system. It has the dual control HVAC, which I don't believe matters, but it will not blow much air on any mode even though the blower is obviously trying. High blower produces a very muffled sound with very little output from any outlet. All modes and temp change when commanded to do so with the controls. This makes for a real bummer on hot or cold days. Any ideas???