_uki_ wrote:at worst, the motherboard
It could always be worse - to replace the heat exchanger.
After firing the furnace, the exchanger heats up very quickly and strongly in two places. These are places where it was suspected that the gaps between the coils are too large. The rest of the exchanger barely warm. It appears that the coil may be deforming, and the cause was probably the freezing of the system.
Theoretically the problem solved.
PS
I think I will add a little and buy a new furnace, at least I will have a warranty and almost a set of spare parts.
