loosing freon dash air

When I bought my 2004 motorhome, the dash air was not working and charging it only worked for a day. In my case, I found it was an o-ring where one of the hoses connected to the heater/A/C unit in the dash. On my Fleetwood Flair, it was accessed by removing the panel under the dash on the passenger side. I was afraid the evaporator core had failed so I removed the entire box (was fairly easy), opened it up and looked. Taking it out I'd noticed oil on one of the hose fittings (as mentioned in an above post). Once I was convinced that nothing was amiss with the evaporator, I put everything back together using new green color o-rings from Autozone. Evacuated the system, recharged it, and after a year it's still working well. I bought a vacuum pump from a national chain tool store, harbor something, a while back and it has more than paid for itself. RVs are pretty easy to fix A/Cs on as all the parts are easy to get at. If you have a hankering to learn A/Cs, it's your golden opportunity! Most likely you have a Denso A/C heat unit. Denso has a great free service manual that even teaches A/C operation. Worth hunting for and downloading. Probably most RV A/C issues are the old o-rings getting hard and leaky.