Nintendo switch Fan issue

I have a water damage switch that I’m trying to repair but cannot figure out what’s causing the fan to run every time I shutdown.

Fan would run normal when system is on. Fan doesn’t run until I play a game and shuts off when I’m not playing.

But I notice when I shut down the system (not sleep mode) but shutdown by holding power button and power option and choose shutdown. This will trigger fan to go on at full blast

Thanks