I tried that myself yesterday, everyone was burning leafs and I didn't want all the smoke but when I switched to re-circulate it flashed a couple times and wouldn't engage while heat was coming to the floor? Didn't really mess with it much and just turned on the vent.
1) 2011 Grand Cherokee Limited Blackberry
5.7L Quadra Trac 2 - IV Towing package
Lux Group 2
20" tires and rims
2) 2011 Grand Cherokee Laredo X Blackberry
5.7L QD-2 - QL- Off-Road II - IV Towing package - Tekonsha P3® Brake Control
P265/60R18 Michelin LTX M/S 2's :D -Volant 161576 Air Intake, Billet Technology catch can