I have an '02 4Runner with the auto climate control. The thing seems to blow hot air into the cabin when I have the AC off and just the fan on. It's not like the heater is on but is in without question warmer then the outside air. Everything seems to work OK as far as the AC and heat working when I want it to it's just the vent function. Is it just due to the air comming over the hood and heating up before it gets to the vents?

 

Yep. This is particularly noticeable when the engines warm, its parked for a very short period, then take off again. The engine heat is simple warming the air before it enters the ducts.