I also heard about running the A/C during winter months to keep seals lubricated. I do that about twice a winter for autos and now the tractor. I cannot find the evap pan but there are two hoses over the rear tires that drip water after using the A/C. I expect that means that there is no build-up in the unit. I took the access panel off of the roof of the cab but found nothing to clean. Again all seems to be working as it should right now. I cannot explain why at start-up this spring I was getting hot air at operating RPM's.