Just a follow up.
I got in to the furnace compartment on the outside. I was familiar with how to get in there by checking it out before when just looking over truck. When we get a new RV, I always take time to try to get in every part. I want to learn the access and what's there before I have to.
When I opened the compartment by removing the exhaust tube first, held in place with 2 screws, and then the compartment hatch with 4 screws, I found lots of moisture. Electric components and circuit boards were wet and dripping water from straight driving rain driving in through the vents.
We weathered a major storm in the unit the night before.
Dried everything with paper towels and wife's hair dryer. I always promise her, I'll buy her a new one if I damage her hair dryer.
Once dry, replaced fuse and no clicking noise. Everything good.
Used "laminate paper", with backing on it, and a couple of pieces of duct tape (never leave home with out it). to create a flap directly over the electrical contacts.
This should prevent direct water impact to circuits, but don't know if it would stop the moisture level in the compartment. it was like pointing a water hose directly at the vent opening.
Ric and Jan Golding
2016 Jayco Seneca 37FS