a/c blowing through defrost vents

[Nimrod]

Buy a cheap cigar, light it up, get a mouthful of smoke, blow it in to one end of any vac line. Watch for leaks (smoke escaping) up and down the line.

This is terrible advice! Pony up the money and buy a decent cigar. A Hoyo de Monterey Excaliber No. 1 with a Maduro wrapper, for example. The Jeep won't know the difference, but there's no reason anyone should suffer through a bad cigar while working on the problem.