What power plant and mods are you using?
You didn't say the magic word.
On topic, really? In deep space, charging the FSD takes temp over 100%? I don't have a Beluga, but I have plenty of ships that the FSD overheats if I don't wait until the ship temp is below 60%. If it's overheating from say 50%, then that would definitely be a problem I guess...
6A, unmodded yet but I'm going to apply low emissions grade 3 of course. Still, you shouldn't need to mod the ship to make it actually work properly.