[BUG] Hotend fan runs slower after 50°C

[dteif]

Hello, I replaced the stock hotend with an original e3d v6 hotend, with the e3d hotend fan. Everything runs perfectly apart from a problem that I'm not even sure is firmware related, but I'll try to post it here.

Everytime the hotend temperature reaches 50°C the fan is becoming clearly less noisy. I checked the voltages of the related pin, without anything connected, and it shows indeed 12.4V below 50°C and 7.4V above. This is explaining what happens with the fan running slower but not why.

I already checked in the firmare I compiled and flashed in Configuration_adv.h and everything seems fine, with the following two lines:

#define EXTRUDER_AUTO_FAN_TEMPERATURE 50
#define EXTRUDER_AUTO_FAN_SPEED 255 // == full speed

I was thinking I can "solve" this problem connecting the fan directly to the power supply, but if you can provide any other hints I would be really grateful. I could even try to help and check in the firmware itself if you could point me towards the right direction.

Thanks for your time and work!

[davidramiro]

Hi there, since you are running a custom fan, you would have to have a look at getting the PWM frequency right.

I wrote about that here: https://github.com/davidramiro/Marlin-Ai3M/wiki/Customization-&-Compiling#pwm-settings

Also, just to be sure, how are you measuring the voltage? A little piece of advice, never measure the voltage while the fan is not connected, because that will certainly fry the fan0 transistor on the board sooner or later. It's kind of a design flaw on the Trigorilla board. If you have to measure the voltage, always do it with a load.

[dteif]

Hi, thank you for replying! I saw some time ago that guide you wrote but I didn't think it could apply to this case, since my goal is to make the fan run at full speed (12 V), and therefore there shouldn't be any pwm involved, being a constant signal. Am I wrong? Also because below 50°C it works as expected at full speed.

I measured the voltage with a multimeter and if I'm correct I did it both with and without the fan connected, but thanks for the advice about the transistor. I didn't know it, and I'm curious about why that would happen.