Water leaking from furnace area

I have an issue with rainwater getting in our motorhome around the furnace. If we have a driving rain that sheets down the side of our motorhome (the furnace side), I start getting water pooling from underneath our cabinets and the fridge. I guess I depends on how level the motorhome is back to front on where the water starts seeping out on the floor. The first time it happened, I couldn't figure out where it came from. The second time it happened, I took out a drawer that is near the floor next to the fridge. Underneath the fridge is furnace. I saw water dripping from the edge of the furnace metal case. It would pool up on the floor and start leaking out under the wood cabinet that is in front of the fridge. At first I thought maybe the water was coming from the vent exhaust pipe but we just recently had a very heavy rain and I felt water on top of the furnace. I posted something about this awhile back and someone mentioned that it could actually be the fridge vent on the roof leaking. I have a residential fridge and I don't see any vent on the roof near the fridge. I did take out the exhaust tube of the furnace and was surprised to see that it angles down from the outside to the inside. I would think it would be the other way around so water couldn't go up the pipe.

Has anyone ever had this problem before? If I have a straight down rain or the rain is hitting the other side of the motorhome I don't have the issue. I have been taping a plastic bag over the vent and furnace box on the outside when I travel now but it looks stupid and I need to get this fixed. I did speak with Thor and they said to call Atwood as the motorhome is out of warranty. I spoke with Atwood and they told me to take it to an authorized Atwood service center. I have made an appointment with a local RV place but I was hoping to be able to fix this myself to save some $$$. Has anyone had an issue with this type of leak and if so, what did you do to fix?

Burch