The last week or so, the wife has noticed a diesel or exhaust smell when we have kicked on the rear heat zone. Since I have a Hydro Hot and there is no diesel in the small rear unit at all, I can't figure out where the smell would be coming from. The exhaust pipe that is connected to the Hydro is completely under the coach and vents out 4 or 5 feet forward of the bedrm. I haven't noticed a diesel leak in or around the engine compartment, plus I haven't run the engine for the last nine days.