These heaters have two modes, thermostat and Hz. Both modes start the heater by testing that the fan turns, heating a glow plug to red hot then turning on the fuel pump to ignite the diesel. Once burning the glow plug is turned off, the fan is ramped up to high where it stays for a couple minutes until it gets to full heat.
In thermostat mode it will stay on high until the set temperature is reached according to the sensor on the controller switch. At that point is ramps down to low until the thermostat drops below the set point where it rams back up. It does not turn off but just cycles between low and high as needed.
In Hz mode you manually set the number of pulses per second of the fuel pump. The range is usually about 1.4 to 5.5 pulses per second. Each pulse pumps .022 ml (depending on the particular pump) into the heater. The fan automatically adjusts it's speed to match the heat being produced. It stays at whatever setting you set until you turn it off manually, or by the timer function, or when it runs out of fuel.
When turned off the heater goes through the shut down cycle which turns off the fuel pump, turns on the glow plug to burn off any left over fuel, then turns off the glow plug and ramps up the fan to cool off then heater. Once cooled off it shuts down completely except for the controller which goes into stand by mode.