Bunk A/C- old vs newer.

The only real difference between your 1993 and your 2014 is that you probably had r-12 in the 1993 and the 2014 uses r-134a freon. Make sure your dash ac is on when you are trying to use the sleeper ac. Not sure about your truck specifically but I do know most trucks now are setup where the dash ac controls the ac compressor.

 

before replacing the expansion valve check 2 things
1. Sleeper air blend door motor... it's screwed down to the top of the evaporator case. Pull it off then adjust the air temp and watch the gear. If it moves, check the door itself to see if it moves free. If either is a no, that's your problem. Stuck on hot air.

2. Sleeper air filter. When you pull it out, shine a flashlight in the box to see if the evaporator is clogged with dirt. I have see em 90-95% clogged. A lot of dirt floats around inside the truck and gets sucked in.

If all is well, now look at the expansion valve.

 

So now I'm curious, would there be an air filter on an 09 Aerocab under the bunk?

 

There's going to be a filter anywhere there is air going through an evaporator. If there's no filter it will fill with mud over time.... if running in generally dusty areas will cake up faster than other areas. It may be a piece of foam, it's a filter none the less. Needs to be cleaned or replaced once a month or so. Find the air intake and you will find a filter... it can't survive if the trash isn't filtered.

 

If the bed is hinged, raise it. If it's not, there will be a bunch of screws around an acess panel under the mattress.

 

While its a nice thought that manufacturers think that through, on the kws at least until 2006 this is not true.

The only filter on the cabin is if someone put one on there after the fact and its only filtering fresh air, not recirc

Similarly the bunk ac has no filter and simply pulls air from under the bunk.

Everything else there is correct, it clogs itself over time and sucks

You mentioned the 93 works great, did you upgrade the front ac box on it?

 

That's not exactly true....
My '97 and 99' 379s both had the filter under the bunk in the evaporator case... my 03 and 05 T600s both had filters in the evaporator case under the bunk.
2005 W900 also had it. My 2009 T2000 has it.... I have spent 25 years in the shop and have owned a lot of trucks over the years - trust me when I tell you that after 1996 there's virtually no a/c evaporator setup without it. It doesn't matter the application. Your house, the pizza shop's walk-in cooler, the 70,000 sq ft mansion on top of that hill over yonder...... EVERYTHING!

R-134a requires high air flow in order to maintain the cooling you expect from it so it requires a filter. R-12 was different, didn't require as high a flow so filtering the air before it enters the evaporator wasn't really a forethought. With the latest tree licker freon, R1234yf.... now that beast barely cools with the sealed system and filters in place. 4 bits of dust and it's like you turned on the heat.

90% of drivers/owners are clueless about the filters. They see that piece of foam caked with dirt and throw it out instead of cleaning it and putting it back in not knowing what it is. It doesn't look like a regular filter.... no frame, just foam.