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


Here is the golden rule for me concerning liquid damage/contamination. Replace the mother board. You just don’t know how far the damage went that is hidden from view. You also run a risk of issues later on when the liquid that started corrosion will finish the job later.

Just to update my solution.

Measurement on the smal resistor was way off. The tiny one between the joycon connector and the BQ chip. Right side reading was correct. Left side was quadruple the amount. Deciding to remove that connector and replace new one. After replacement from donor board. Switch is function as normal with no fan issue

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Thank you for the Solutions, i had the same exact issue. do you mind letting me know how to test the resistor with a multimeter?

Set multimeter to diode mode. Then ref prob to ground and black on one of of the resistor,

Here’s a map of diode reading in that area, diagram thanks to Calvin in this forum

It was the one that’s reading 550 and 524 bottom right of chip

Also check fan connector too , Had another one where contact was crossed on one of the pins and cause that too.

Thank you so much for the diagram, i will give it a try to see how it goes.
If i had questions again, might i ask you again?

Thank you