RV Repair: Duo Therm AC, keystone sprinter, duo therm ac

Question
I have a 2004 Keystone Sprinter that the AC does not work in.  When I turn it on with the thermostat it is cold for about 5 mins.  After that it starts blowing unchilled air.  I have check the thermostat and the relay in the AC unit.  Both are OK.  I was told to clean the coils with no success.  I have notice that the line from the compressor is frosted over.  It is frosted all the way to the filter dryer.  I was wondering if that could be the problem.  Any other ideas.

Thank You

Answer
Hi Ron:

Is there a good air flow coming out of the supply vents? Does your RV have ducted air supply in the ceiling, or just blows out at bottom of air conditioner. You stated you cleaned the coils. Did you clean the evaporator coils or the condensor coils, or both? If you can locate a thermometer that will read down to 40 degrees, place thermometer into the supply air grill, and let me know the temperature of the supply air, also need to know the temperature of the room. The line leaving the compressor, you stated it is frosting up. Is the a line approximately 1/2 inch in diameter? Is there a filter drier installed in this line? Can you tell me the BTU rating of this unit? If not please send me the brand name and model number.

I will be glad to assist you in anyway possible. I will be awaiting a reply from you.

Regards, Larry