Turn off part cooling fans when klipper is booting / offline

[ivory magnet]

Hi guys,
I have V-Core 4.0 with IDEX and can not figure out, how to turn off the two part cooling fans (4028) until the klipper boots up. They go on full blast for a minute or two in the beginning, when klipper is offline (no PWM signal). There is this guide in the documentation https://os.ratrig.com/docs/guides/4028/#my-fan-runs-at-100-until-klipper-boots, but I can not make it work in the current setup. Klipper neither accepts "shutdown_value" in fan section, nor "enable_pin" works due to it being used multiple times. I have a standard IDEX setup/kit.
Is there a way to turn these fans off in configuration, until klipper boots up or do I have to rewire the fans (GND) to do so with Octopus board?

[violet cobalt]

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[uneven obsidian]

The 4028 fans are "smart", in that if they don't get a PWM signal, then they will run 100%.
In order to get them to stop, you need to only allow them to consume power once the PWM signal is available. So just like you realized, you'll need to remove power or ground to the fan, and that guide shows using the heater port gnd to do that.

I haven't investigated if/how to do that via the toolboards. I also son't have the my printer in the same room, nor do I turn it on/off very often so the inital noise doesn't bother me

[exotic yarrow]

I don't see the edits you tried to make in your printer.cfg (ratos.cfg should NOT be modified). Please upload the one that gave you an error

it should be similar to

[fan]
pin: !fan_part_cooling_pin
cycle_time: 0.01
enable_pin: PA3

with PA3 being this one marked in RED

[ivory magnet]

Hi blacksmithforlife,
thank you for your reply.
I have understood now, that rewiring the part cooling fans (connecting ther black (GND) wires to the PA3 pin ("-" of HE1) ) is the only way not to have them on full blast, when klipper is offline.
So I rewired everything as you and the documentation described (both fan GND wires to PA3) and now I get "Sensor 'heater_bed' temperature -59.500 not in range" error message. Do you have any idea, regarding what I have done wrong?

[exotic yarrow]

probably bumped something and connection came loose

check your thermistor wiring for your bed since that is the one that is complaining

[ivory magnet]

You are right. Sorry for the dumb question. I have indeed unplugged the bed thermistor cable...
Thank you for your help and patience. (: