Hardware Fan and Joycon issue

[Mightyjebus]

I'm working on a switch that works fine apart from the fan doesn't spin and the joycon's don't charge. The joycon's get recognised and pair with the switch however they don't charge when attached to the switch. The joycons also work unattached from the side of the switch.

Things I've tried so far:
changed joycon's - same issue
changed joycon rails on both sides of the console - same issue
changed the fan (3 different known good fans) - same issue
changed the PU chip 3 times from donor boards - same issue
changed the 3 pin IC just above the PU chip - same issue

When I plug the charger into the switch while looking at the controller screen on the switch the charge icon flashes up for a split second underneath the controller and then disappears.the switch is running the latest Nintendo update 10. something.

Any ideas what could be causing this?

 

[Mightyjebus]

if it's any help on the 4 pins on the fan connector I get the following:

Pin 1 0.4v
Pin 2 0v
Pin 3 1v
Pin 4 1.2v

On a working switch I get (with the fan spinning)

Pin 1 3.9v
Pin 2 0v
Pin 3 1.6v
Pin 4 1.6v

If my thinking is correct Pin 1 and 2 are the + & - lines for the voltage to drive the fan and pin's 3 & 4 will be fan speed and fan speed control.
Looking at my measurements it looks like the +v isn't getting to the fan. Apart from the PU IC is there another part of the motherboard that is common to the fan and joycons that produce or control voltage?

 

[Mightyjebus]

so a little further forward on this. I was checking for shorts on the caps when I found some corrosion in and around the underneath of the Max chip. I gave it a clean with IPA and then blasted the area with the heat gun.

Now I get the fan spinning when on however it also goes to maximum speed when the console is switched off and would probably run until the battery is drained. interestingly when you switch the console on it stops spinning like a madman and works normally.

I've got a load of components with dry/corroded joints that I now need to go and reflow individually oh and the joycon's still don't charge but I now think it's liked to something in the area with corrosion.

 

[Dr_Mo91]

Hello, I am having the exact same problem so what would you recommend that I should do? Regards