Fan comes on during extrusion after print

OK, I have a MKS 1.5 board, which is supposed to be a combination Arduino/Ramps board on a delta printer. The board has a non-controllable, always on 24 volt outlet which is used by the cold end fan and a separate layer cooling fan which is attached to the fan terminals. This is a bowden setup, so there is no co-location of the fan wires and the extruder stepper wires once they leave the board area.

1. The board is power reset completely
2. The hot end is heated
3. Using the front panel, a little filament is extruded. No movement is seen in the cooling fan.
4. A small print is done.
5. Using the front panel, a little filament is extruded. This time, the layer cooling fan comes on whenever the extruder is run, and it stops when the extruder stops.

I am having extrusion problems. I thought, "maybe the extruder is having power robbed from it to run the fan".

So I reflashed the software, yesterday, using the stable version of repetier freshly downloaded. And just to be sure, since I thought I had a bad extruder motor, I swapped the extruder driver in the firmware to use the E1 controller rather than E0 and moved the plug. It still happens.

Is this intentional? A bug in the repetier firmware? Is there any case where extrusion could turn on the layer cooling fan? Or is this some sort of hardware issue on the board?



The forum thinks I am a bot. I am not a bot.

Making sure I get e-mail, sorry.

I asked this elsewhere, did not see anything appear for what I thought was a long time, and reposted it here - then it appeared there. The thing I observed is not actually causing me a problem. I thought it might but it was not - I sorted the problem without addressing this. So, I am not worried about it, if this is happening, I don't care.