Fan keeps turning on and off.

Having a small fan issue which I think the problem is in my code. While printing my fan keeps turning off then turning back on (it seems to turns off when it changes layers). After it turns off I have to keep sending M106 to turn it back on. I want it to always be on but I think I don't have that declared in my code. Where whould I edit that? Running Marlin firmware.

Edit: Also I've added the Mcode for the fan in my Slic3r program. Still has the same issue.

Edited 2 time(s). Last edit at 08/21/2015 03:51PM by MrMeeeseeeks.

Solved it. In my Slicer I had the Fan Min 35% and Fan Max 100%. I changed the Min to 100% and now it's always on now.

Which fan is this? If you want the fan to always be on, you can just wire it with the input from the power supply so that it gets a constant 12V when the printer is turned on. No need for the Arduino to control the speed.

If this is a fan cooling your prints, then you don't necessarily want it on all the time, especially for the first layer or two of PLA or when you are printing ABS.

If the fan is cooling the fins on your hotend, then it is a good idea to have it on while your hotend is hot. However at least Marlin code should have an option under the configuration_adv.h file for turning the fan on at 100% when your hotend is above 50 degrees (default). The fan will also continue to stay on after the print is completed until the hotend cools down to less than 50 degrees.

Not sure about the configuration_adv.h settings for cooling the stepper drivers. In that instance my fans are also stopping and starting somewhat randomly.