I have a similar event in my '87 244, the cause of the leak is due to a rust hole in the lower left corner (driver side) of the windshield. This was discovered when I was replacing the windshield. Adding some sealant (waterproof) remedied the problem to a degree - it still leaks but not as much. I assume the hole was not completely sealed. I don't think that changing all the fuses are necessary; I'd carry a spare set with you but if there is a short, i'd be more inclined to think the problem would be further up the line (fuse box, etc.). Good luck.