PWM fan not turning off

Laszlo Kozik

Been using duet for a long time now and this really puzzles me
just installed a 4 pin PWM exhaust fan on my printer , everything seemed OK for at start.
was able to control the speed of the fan no problem but then i wanted to turn it off with M106 P4 S0
but it just wont turn off , keep running at minimum speed
Hope someone can point me in the right direction

The firmware and board I'm running is
RepRapFirmware for Duet 3 Mini 5+ version 3.4.0 (2022-03-15 18:59:15) running on Duet 3 Mini5plus WiFi (standalone mode)

the config setup is

;Exhaust fan
M950 F4 C"!out4+out4.tach" Q100
M106 P4 S0 H-1 C"Exhaust Fan"

tried different Q values but no effect

Thanks in advance

Laz

Phaedrux

Can you try a different fan output in case it's the mosfet? Is it able to control speed? Just not turn it completely off?

Laszlo Kozik

Yes I tried both out3 and out4 and yes i can control speed just not completely off
had a 3 pin fan on before that worked fine and was able to turn it off but not the 4 pin

I know its strange

Phaedrux

Ah I see. Well some PWM fans don't seem to allow for a true off.

Can you test it as a simple two wire connection and use the Duet PWM and see if it will turn off completely? You lose the tachometer read out though.