maybe its a wrong fan bc when I touch it in the middle its hot!
@MooseJuice @brent113 did i do the wiring right or is it something else? Sry for the @ but no one is answering
Yea, with the pictures posted it’s basically impossible to tell you what’s wrong. Basic troubleshooting applies here.
Does the fan work in isolation
Does it work with the splitter
Does the fan work along plugged into the board
Does it work on a power supply
Is it a gcode issue
Is it a hardware issue
Do you have another fan
Do you have a multimeter and can verify wiring.
I don’t see a flyback diode, is that present.
Did the driver circuit overload and die
@brent113 you still running your snappy with the fan mod? I have come to realise today after numerous attempts at printing the Benchie boat that the overhangs keeps curling upward which I think is as a result of poor cooling.
Sry for this. when i plug it in like shown on the pic the fan does not work, but i noticed that it gets hot and you can not spin it. I dont have a diode or a other fan.
@Somnium It sounds like your fan is receiving power then, but just not spinning. If you are able, check to see if the fan spins at lower voltages, or while it’s plugged in quickly starting to spin it and see if it continues to spin. Something stefix found earlier in this thread was that his fan would cut out at the 24 volts the print head supplies. If this is the case, it could potentially be fixed with a resister, but I’d wait for someone else’s suggestion to reduce voltage as I am not extremely experienced with electronics.
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How can i reduce the power?
Yeah i tought of it too that its just a false labled fan.
Don’t listen to me, I don’t know electronics well. 
You cannot simply use a buck converter in this application as the fan control is PWM. You would need a level shifter as well.
A much easier solution is just don’t run the fan at 100%. The inductance of the fan will smooth out ripples and 50% PWM will give you on average 50% of the voltage.
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Ok i will try this the command for this should be M106 S126?
Hi Thalik,
I’m having the same issue as you. Fan turns on full as soon as the snapmaker is powered up and have it connected to the same port (Fan1).
Were you able to solve it? I’m wondering if we’ve done the same thing.
@Kataan My Fan 1 is always on, right from the moment printer is powered on and not reacting to M 106/107 commands. That is - with or without additional fan connected. For PLA this full blow was fine, but for PETG/CPE didnt work so well, so I “solved” it by inserting a switch with which I manually disable additional fan for the first layers or PETG.
I suspect that there is something wrong with this (newer?) printhead and I should engage with Snapmaker support, but couldnt be bothered as just switched to another 3d printer…
I have performed the mod on the newer toolhead, everything works as expected.
This is my second time doing it, I got the diode the wrong way the first time and fried something for the fan, disabling it permanently. I hope you have not done something similar, but permanently enabling it instead
Hi all just to confirm, both fans once on the splitter will benefit from the diode right? i.e the connector connecting to the PCB has the diode before the split running to the 2 individual fans?
Doesn’t matter, basic electronics law with the paralleled equipment, order doesn’t matter and the diode will protect the entire circuit.
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Cheers Brent, building my splitter whilst waiting for my connectors to turn up on Wednesday. Printed the blower off and have the fans in hand
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Anyone with the new toolhead, perhaps they switched fan 1 and fan 2? Have y’all tried plugging the 5015 into fan 2?
That diode also allows current to flow through the load longer. This can be problematic with PWM. A better solution is a zener across the fet, with the zener rated for 10 to 20% less than the max drain-source voltage rating of the fet. Both protect the fet but the zener allows the pwm to shut off the load faster.
That’s beyond my knowledge in this type of application.
Both of those sentences are not obvious to me why that is the case. Could you elaborate? Does the inductance of the fan not smooth out the PWM transients sufficiently?
Sounds like you have more knowledge about this than I do, so question: My understanding was zener’s do not have a particularly sharp IV breakdown response so a 10% lower rating would not sufficiently protect the FET at high peak currents. Also, don’t zeners have a slower response than other diode types and are not typically used alone in flyback applications as they will have a higher voltage peak before clamping? I have seen them used along with a flyback diode.
All that being said though, I measured ~65V peak response, so a zener in this application rated at 90% of the FET absolute maximum would never trigger and it could be argued the diode is not needed at all.
I don’t like operating switching FETs at 90% of their absolute maximum rating so it was a judgement call to put the flyback in.
Also, the FET is on the PCB and using a flyback diode doesn’t require PCB modifications, or is there better location for the zener?
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You can not instantly stop current in an inductor. If the fan is an inductive load (not sure it is, actually) then when the FET turns off, the voltage on the drain of the FET will skyrocket unless something prevents that. The conventional flyback diode does that by allowing the inductor’s field to collapse and put that energy into current through the inductor. Where else could it go? As long as that current is flowing, the load is still on.
You don’t need a particularly sharp response.
I don’t know why you say the zener wouldn’t trigger. We’re not talking a 1.5 MHz SMPS here, but rather PWM at 10’s of kHz.
What’s the VDS rating on the FET?
Those max ratings really working numbers, the FETs are typically tested a bit higher than that actually.
The fet (depending on the part) may also include a D-G zener to turn the fet back on if the drain voltage gets too high.
I used this approach in many designs, it works very well, and as I said it speeds up the turn-off.