I followed your excellent guide and on reassembly, the fan doesn’t cut in now.

I cleaned it using compressed air.

I disassembled it again and while on the bench measured the power at the pins for the fan at 0.3 V.

Fan requires 12V DC. Tested fan with generic 12V power adapter. Tested good.

Reassembled and still no fan sound and brick is getting quite hot. While on bench, LED was lighting orange.

I cannot find any reason the fan will not run