Basic Information:
Printer Model: HEVO
MCU / Printerboard: Bigtreetech Skr 1.4
klippy.log
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Describe your issue:
Hello,
I hope I can make my problem clear, if not please be kind. 
So I use this mainboard
no picture because I’m a new user
I connected the coldend Fan to Pin 2.3. For further connections I use the Piggyback 36. See here:
no picture, because I’m a new user
The switches are set to FAN1+ - VCC and FAN2+ - VCC.
FAN2 goes to PIN 2.3.
The cooler both work. Fan1 is working as printpart cooler and works.
Fan2 should start at 50° see here:
[heater_fan Extruder_Fan]
pin: P2.3
heater: extruder
heater_temp: 50.0
fan_speed: 1.0
But it won’t. It only starts, when the temperature should sink. It also changes the way of blowing. So it’s not a steady blow, it’s more like PWM, what I don’t want for the hotend coldend cooler.
This makes troubles with the PID and keeping a steady hotend temperature as well, see here:
What I did so far:
I changed the wiring of the red and black cable at the piggy back. If I do that, the cooler doenst work at all.
I changed the cooler physically and changed it with a different one. Same result.
Any clues?
I thank you beforehand for helping me.