Fredxx expressed precisely :
In this case the fuse is in series with the thermister.

I suspect the problem is whatever was plugged into CN3.

You might be correct, but I couldn't think of anything representing a
load that might be part of a PSU. Without trying to trace out the
tracks, might CN3 be a mains on/off switch, or even a mains powered
neon warning light?

I have a scooter and its SMPSU in the hut. That PSU has a cooling fan,
I wonder if this unit also has one? The fan only runs when the unit is
doing a rapid charge.