The 12V LED keep on even Boost_EN low

[kscccc]

The 12V LED keep on even Boost_EN low.
It should be better by using Boost_EN pin drive the LED.
or
Add a PMOS/Load switch on 5V before Boost IC Vin to totally cut off the supply.

[ansemjo]

Well, yes, you're absolutely right. :P
For some reason I thought that disabling the regulator would turn off the 12V supply altogether – which is, of course, not the case due to the straight path through the inductance and diode.

I am currently in no real need for a new luftctl PCB .. do you want to make one with the above already fixed?

I'm thinking that having the "choice" between 5V and 12V is a "feature". But I know that some fans do not completely turn off, even at 5V and zero duty cycle .. so yes, an additional load switch seems like a good idea.