We are not a DP, so I would assume systems are different. But we have been trying to get our dash air working, after the PO indicated "it never worked well".
The MH has spent the last couple days at the shop. "It never worked well" turned out to mean:
1. It had no reefer.
2. Upon trying to fill with reefer (134C), the maintenance port was leaking.
3. Upon repairing the maintenance port leak, turned out the compressor was bad.
4. Replaced the compressor, filter drier, expansion valve (everything comes in a kit now, from the story I was lead to believe). It took (3) total parts to get the correct filter drier. The expansion valve is "close", but piped a bit different.
5. Tried to replace the condenser - it also came in the "kit".
A. 1st was the wrong physical size - too tall, not wide enough. 2nd was the wrong physical size - too wide, not tall enough.
After a couple days of this I asked them to please just use the old one - although their warranty is only valid if ALL components are replaced.
B. So instead they had "the condenser shop" pressure test the old one. Installed it, and ...someone...had apparently dropped it or something, as there was now a reefer leak on a u-tube. Pulled it again and they repaired the leak, reinstalled.
C. Went to install the oil cooler lines, and (my guess) is the mechanic tightened the connection a bit too much, and cracked the oil cooler fitting that is on the condenser. Pulled it again, sent it back, repaired, and installed again.
6.Tried to charge the system and it would only take about 2/3 what it was supposed to. Several hours later (with me sitting on my posterior in a waiting room...
) , they found a pair of check valves installed in the fitting between hose and (I think) filter drier. One had disintegrated, putting some parts in the filter dryer. Removed both check valves (apparently a "better idea" at some point in time that did not work out). Bought a new filter dryer. Installed. Filled with reefer. Got it mostly balanced. removed, pulled a fresh vacuum, and topped off again.
7. It now works. Kind of. In 100F weather driving home just now, it was maybe 70F. I am not real happy. I still have more heat coming in through the firewall than the AC can keep up with. Once I stopped driving at just sat there at idle, you could just barely feel the dash air working.
They did appear to be doing their best, and they asked when I can bring it back. Unfortunately, I am days late in departing on a x-country trip, so it looks like it will be with crappy air...
I wish you better luck then we have had.