[SOLVED / FR] Hotend fans on until Klipper fully boots

This is mostly a safety feature, that should ideally never be needed, but would be very welcome in case you need to quickly change config with a hot hotend and klipper won’t boot because of an error in the config.

I’d love to see an option, where the hotend fan is always on when power is provided to the main / toolboard. Right now, let’s imagine something happens during print, the printer reboots, power out, etc - the hotend fan will only start blowing when klipper fully boots and starts reading the temp from the thermistor. If the delay is long enough, we’re looking at a clogged heatbreak as the easiest problem, to a completely melted hotend mount if it gets worse.

So to make this simple - can we have hotend fans be on by default, until klipper boots and sees that there is no need for the fan? :slight_smile:

That capability is available now.

When you create your Klipper image, specify the fan pin in make menuconfig as part of the “GPIO pins to set at micro-controller startup” option:

It will work on a main controller board, or a toolhead controller (connected by CAN as I show above).


Hot damn, that’s cool. Thanks for showing me how to do it. I’ll test over the weekend :slight_smile:

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