Thanks to everyone for your replies. I am sure that the leak is internal from the drip pan to the inside of the coach. I have been thinking for the last 2 years that at some point I would have to replace all 3 A/C units. So now is the time. I have had issues with the center air not working proiperly at times, and the rear air has trouble starting on occasion. So I have an appointment to get all 3 airs replaced next week. The bus will be 12 years old in May and little by little I am replacing any item that seems to be reaching the end of life. It appears that I will have this bus for a long time and I consider this a step in making it more reliable and enjoyable.