I've got a '07 Silverado crew cab LTZ with the passenger controls for temperature. Recently I noticed hot air coming from the passenger side vents (and the thermostat for that side was at 60 like the drivers side) and the flow of air is less than the drivers side. I checked all of the obvious settings (at least I think) ac on/temp setting/vent position. Isn't there a separate fan for the passengers side that might be going out? It has worked since then but has failed once or twice and just blew hot air. Any trouble shooting tips?
Thanks in advance...

 

Idk about your model but my 98 there is plastic hosing going to the vents. Maybe you have a hole in the tubing or maybe it is slipping off. Did you try to look behind the vent to see any obvious or any non obvious things wrong? Do you hear a whistle from that side when you turn the heater on ?