24v PWM fan at 100% only outputs 4 volts when fan connected

wittj2

I have my part cooling fan on fan 0. It has worked for 6+ months. yesterday I it stopped working. My hotend fan is still working. I checked voltage on the pins and it is 4 volts with the fan connected and the fan at 100%. when I disconnect the fan I get 24 volts. I have tried multiple fans all act the same. I am using 2.03 firmware. This is what I have in my config file for fans

; Fans
M106 P0 S0 I0 F1 H-1
M106 P1 S1 H1 T40

; Tools
M563 P0 D0 H1 F0
G10 P0 X0 Y0 Z0
G10 P0 R0 S0

I have tried to remap the part fan to fan 2 using

; Fans
M106 P2 S0 I0 F1 H-1
M106 P1 S1 H1 T40

; Tools
M563 P0 D0 H1 F2
G10 P0 X0 Y0 Z0
G10 P0 R0 S0

No luck . I have also looked at the board I don't see any issues with the board any ideas?

Phaedrux

You don't mention what board you have. Does it have a blade fuse near the fan ports? if so check if it's still intact.

Also check the mosfets near the fan ports for damage. Post a close up well lit photo if you're not sure.
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wittj2

@Phaedrux

Did not notice that on the 1st mosfet. Are they replaceable? I have tried to map to the 3rd PWM for my part cooler but I have not had any luck. I posted what I tried above.

Phaedrux

M106 P2 S0 I0 F1 H-1

Are you sure you had F1 before? That's the PWM frequency, so F1 means 1hz. Remove the F1 entirely to let it use the defaults and test again.

https://duet3d.dozuki.com/Wiki/Gcode#Section_M106_Fan_On

Phaedrux

@wittj2 said in 24v PWM fan at 100% only outputs 4 volts when fan connected:

Are they replaceable?

It must be a bad day for mosfets. Yes they are replaceable if you have the soldering skills. I'm not really the guy for that unfortunately.

dc42

There are lots of videos on YouTube showing how to desolder SMD components without a hot air rework station. The mosfet package is SOT23-3. If you haven't done this before, practice on an old hard disk driver or other scrap electronics first.

For the replacement part number, see https://duet3d.dozuki.com/Wiki/Connector_and_spare_part_numbers#Section_Fan_mosfet.

A Former User

Can help to (temporary) remove the plastic part of the fan header to get you easier access to the last ~~pin~~ pad; but they're usually not easy to remove without a little heat as well.