No, all of the electrical components are at the level of the box or higher, that would be a seriously wet crossing and above what I use the truck for. I would only run into problems if I try to “swim” the truck, however, at that point I would be worried about my engine intake over the heater.
Also, I sealed all of the provided connectors with electrical grade silicone to make them waterproof. and I sealed all of the pass through from the box to the exterior to protect the heater unit.
Finally, the combustion air intake is up above the wheel well to keep it protected from spray, and I added a u bend like a snorkel as a precaution.
Regarding mud, as you can see in the photo everything is well sealed and protected. (You cant even see the combustion air intake above the fuel pump). My cold air return is just pulling air from the inside of the truck so I am not making the heater work harder by trying to always heat air from outside temp.
