The FBH if the outside temp. is low enough doesn't shut down even when the coolant is fully warm it goes into idle mode
72C = part load operation, anything above 76.5 the control idle mode cuts in, if the temperature drops then drops below 71C it will resume part load operation if the coolant temperature drops further as a result of heavy demand from the vehicle heater the FBH will resume full operation at 56C.
Shutdown proceedure after engine switched off:
175 seconds full load operation, 100 seconds part load.
Hope this helps.
Russ