[Carl n Susan]

If the 2002 Mountaineer is the 5th wheel variety and not a travel trailer model, I am pretty sure it had an underbelly cover at one time.

Heat to the underbelly tanks is kinda hooky. Behind the back wall of the passthru should be a flexible hose from the heater that runs down into the general area of the tanks. That is the heat source.

I haven't seen a Mountaineer in many years and never really examined one. There are a few members here that have, or had one, and hopefully they will answer up.