RV Repair: Duo Therm Air Conditioner, trouble shooting guide, duo therm air conditioner

Question
I have two brand new units mounted on a Grand Junctions 5th wheel.

The one was used only once and was very cold.
Now I turn on, only hot air.  What happened?  I removed the cover on roof and noticed that all tubings were hot.  What ya think?
Can you provide me with a trouble shooting guide?

Model#  630515.331 / Serial Number - 53135505

Answer
Hi Richard:
Sounds to me that the expansion valve inside the unit is not working right. If the smaller line coming out of the compressor is hot then the compressor is working right. The return line, larger line, should be cool coming back if it is not it is because the freon does not expand inside the unit. That is a function of only the expansion valve. I have not seen many go bad but it is possible. I could write a detailed trouble shooting guide but it would be faster to get a manual from Duo Therm. Good luck.
Bill