APU Evaporator Fan Mod

cold air sinks, heat rises, cold air comes out the bottom so it can accumulate from low to high and push out the heat. if they shot it out the top directly you would lose 20 degrees by the time it mixed. all you need is a little fan to get the cold air up high, I use this one, it can swivel point straight up or set on a bucket right at bed height, about the size of a basketball

 

I had a 2018 Peterbilt 389 with a Thermoking TriPac and the bunk A/C was plumbed this way when I got the truck. When the APU was running the A/C would not keep the sleeper cool at all with the cold air coming out of the floor vents. I made my own duct plumbing and eliminated the floor vents and routed the air to go through the sleeper vents and the A/C worked so much better. I spent a total of about $40 on parts at my local hardware store to make my own A/C duct work. It was well worth it.