Might try here....
http://www.cumminsforum.com/forum/technical-service-bulletins-recall-support/76521-air-conditioner-problems.html I copied this off of the forum:
"blows cold for about 30 mins, after traveling and time goes by the air coming from the fan thru the vents gets weaker and weaker. then coming from houston to san marcos i stop for the night, get back in the next afternoon start her up and the compressor is in and out ever 10 seconds, indicating low freon in the system.
after some snooping i also find that the evap. coils are half clogged with algae. this is defiantly blocking fan circulation. this explains why my truck always smells musty when i turn the AC on. i thought it was just the smells of the drilling rig getting in LOL.
tonight i will be tearing everything apart, diagnosing everything i can, cleaning the evap coils with some special cleaner foam and some compressed air and then off to a shop to check freon levels tomorrow and hopefully she is just a little low."
