RV Repair: A/C problem, fan mode, purple wire

Question
I am renting a 5th wheel with a Chillegrille (Coleman-Mach) A/C unit 8330-63, 8530-63 (not sure which model).  We started renting the unit last week and the A/C was working fine.  Then my wife noticed that the A/C was set at 69 but the thermostat was reading 78 and the A/C was running hours on end.  I tried setting on Auto and Hi Fan mode but both ways the unit continued to run or didn't bring the temp down.  I'm not sure if there is a better site to trouble shoot and the installation manual that came with the camper doesn't have a trouble shooting section.  I am concerned because my wife spends most of her day in the trailer with our pets.

Answer
Quentin, The best way to test the ac is to open the bottom grill and look for the purple wire. That should be drawing around 12 amps when it is running. If it is nowhere near that then the charge has probably been lost. You should have the fan on auto unless you want it to run all the time. Also when you have the bottom pulled down check to make sure that there is no refrigerated air getting into the intake side. You can feel up in there and you should be able to tell if there is cold air going up in there. The last thing I would check is to see that the condenser coil is clean and that it isn't freezing up on you when it is running. I hope that this helps, Bill