La Mesa RV, where I had the leak located, was NOT keen on having me in their work bays, but technician was kind enough to send me a picture of the offending bubble via his cell phone. So, the mystery is over! It’s what I least expected. It was the tiny little solar panel used to “top off” the two starter batteries. (The batteries used to start the diesel engine and the generator engine.) There is a tiny opening about a quarter inch wide where the water would enter and flow into the roof creating a potentially large amount of damage and expense.
Remember this roof picture…it shows the tiny solar panel. How much did it cost to locate and fix this little bubble bandit?? $275.00!! But, this “Bubble Test” could have found many more openings where rain water can enter an RV. It’s a small price for the knowledge and repair.