2002 Jeep Wrangler

My 2002, 5spd, wrangler w/ 77K is doing basically the same, but works intermittently w/ much play. I found this information:
Question: "We have a '97 Wrangler and the defroster does not work. The heater kicks @#$ on the floor and dash. But when we switch it to defroster it does not switch to the windshield vent. The defroster vents for the passenger/diver windows work. Is there a way to check this and repair it?"
Answer: "The heater/defrost control "doors" are controlled by vacuum, check under the hood and find the small vacuum line that goes thru the firewall and make sure its attached to a vacuum riser on the motor. Check under dash at or around the heater box for broken or disconnected vacuum lines. "

I think I found a vacuum line against the firewall that is cracked on the bottom. But I haven't gotten it looked at by another yet.