Diesel heater?As you're supposed to let them shut down fully, they are often not wired through the isolator
In standard configuration only the autopilot and the charger are directly connected (over separate fuses!) To battery plus side. If not sure, disconnect the wire from terminal and look which function is missing. Work with caution only with isolated tools, shorts on terminals could be dangerous!
No! 100% it is not diesel heater.
I think that the red cable (nr 2) comes from the alternator