I have an old soda machine I've salvaged that won't cool properly. The compressor kicks on and cools the cold plate, but after 3 hours it stops cooling. I can repeat this over and over -- if I turn it off and then turn it on later it does the same thing -- cools for the first three hours but then stops cooling. Could this be a lack of freon (and a freon leak) or is this likely something else? Help. The compressor is depicted below. It has been cleaned and repainted (the 3rd pic).