2012 Cascadia sleeper ac not blowing cold

Is the front a/c working good you can feel the ac lines under the bunk and in front of cab but front ac has to be on for bunk to work and if low on Freon bunk wont work and cab will just not as good depending on how low

 

Freeon may need recharge.
Or, the Air conditioner compressor can be out - the thing that regulates the Freeon - then it needs to be replaced.

 

There's a million and one different things that can cause an AC to function inadequately. People like to assume that it's always refrigerant in need of a recharge (and, by the way, if you're already losing refrigerant in a 2012, you have a leak, and recharging alone will only be a short term fix). Blockages in the system, bad metering devices, insufficient airflow through the condenser fins, clogged evaporator, jammed blend doors... that's just the tip of the iceberg. It may also be possible that you have too much refrigerant... that causes excess system pressure, creates a low superheat, and the heat exchange doesn't go as smoothly.
You need to have a shop to a full system performance test. They'll read system pressures with a manifold gauge set (it might seem archaic, but it really does a lot to narrow down the problem), evacuate the refrigerant, audit the weight of the evacuated refrigerant against what's supposed to be in the system, recharge it to the appropriate amount, test system pressures again, and then do a leak test on the system. That's how it's supposed to be done, and also why AC systems really aren't a DIY thing.