On my Victron charger the red alarm lamp seems to cover several faults, Looking at some of the manuals it also seems to be the same on some of the inverter chargers.
My alarm came on last week and it was low voltage on the voltage sensor lead caused by the fuse in the engine compartment being partly dislodged. Disconnecting the voltage sensor lead in the charger worked until I traced the problem.
Nothing to do with temperature so worth checking.
Paul