The cabin heater runs on diesel from the same tank as the engine. It has a separate valve from the dieseltank (just beside valve for the engine. The heater heats up a small tank of hot water (not the same as the hot tap water tank). The hot water is circulated to a separate heater for each cabin and the saloon. These heaters has a fan blowing hot air heated by the warm water. Each room has its own thermostat.
The heater is controlled by a knob at the corner of the couch in the saloon. This knob has three positions. The middle position is off. Turning it clockwise starts the heater. It will take a few minutes before the fan in each cabin / saloon kicks in. Turn off the heater by gently turning slightly counter-clockwise to the middle position. The heater will still run for a few minutes to cool down.
Please note that the heater generates hot exhausts on the outside. Ensure nothing is too close.