[dsraven]

when using the AC in the summer most techs will say to use the inside air option because the AC dries the air as it goes through the evaporator inside the unit. this makes the moisture collect as frost on the evaporator. when the AC compressor cycles off for a minute because it has reached the temp set point the frost has a chance to warm up and melt off. this moisture is drained to the outside and is the reason why there is a puddle under the front pass side of a modern vehicle that runs AC in the summer. eventually the ambient moisture has been collected and drained except for what you are giving off personally so the system works better. when using the outside air option in the summer it is usually because it is hot outside. hot air contains more moisture than cold air, so if you use outside air option the AC evaporator is always collecting moisture and is also using warmer outside air to try to cool things off instead of the already partially cooled interior air. for that reason I would say you likely don't need anoutside air source unless you plan to use the truck year round where you have snow melting off your shoes etc. in more modern cars the AC runs in the background to help remove some of the moisture in those cases, thats why you will hear the AC compressor cycling in the winter and wonder what the heck, it;s minus 30 out and the AC is trying to operate?