I've noticed this most of my time owning a 08.
Air temp is set on cold.
AC off.
Fan on.
Fresh air in.
Car sits in the sun, 70-90+deg day....
I start driving, and the air coming out of the vents is NEVER cool. Sometimes, even after an hour drive, the air is still hotter than outside.
I can turn the AC on, and it cools the air for awhile, then I shut it off, and the air slowly heats back up to hot.

Normal cooler days, 60 and below....the air just isn't HOT coming out....so it's not like the thermostat is stuck on heat.

you'd expect the ambient air temp would equalize the vent tubes and everything, so sooner or later, ambient temp would come out.

So, what gives?