Hydro Hot system Question - works sometimes?

The HydroHot is the smaller of two systems build by the AquaHot company. The system consists of a large pressure tank containing a type of boiler fluid. Inside that tank is a fresh water loop which heats water by heat transfer from the heated boiler fluid. There is an optional engine coolant loop also which can be used to preheat the engine and also for the engine coolant to heat the boiler fluid while driving. The diesel burner should be left on at all times and in the primary heating source for the boiler fluid. It sounds like yours is not lighting. The sound you hear is the blower motor that provided combustion air to the burner. The diesel burner can bring the boiler fluid up to operation temp in just a few minutes. The electric element is mostly to maintain temp after the diesel burner gets it up there. The electric element is just about 1500 watts so it would take hours for it to get the boiler fluid up to temp. The times there was warm water available may have been shortly after driving when the engine would have added heat to the fluid. Or the electric element may have been left on and kept the temp up. This system is also the furnace for the coach and provides heat in cold weather.

The normal service required is replacing the fuel filter and the burner nozzle. It would be worthwhile to find a AquaHot certified service tech to do a service on the system and explain its operation to you.