I had the compressor lock up, redid the whole thing and changed to the new R134. It was pretty expensive, little over a thousand dollars for everything, including labor. I think I know what you are talking about on your system, it seems like it is either too cool and then when you turn it down it takes longer than what I think it should to start cooling again. Mine is a 1991 model. According to the mechanic that does some work for me, JD improved the air conditioning system on the later models, don't know what year this took place. Compared to the trouble I had with my other combine, this is something I can put up with and I doubt I will spend more money to update to the newer system.