Is my part cooling fan haunted ?

Hi there,

I'm using a modified Anet A8 with auto leveling and a RAMP 1.4 board. Marlin 1.1.8.

My part cooling fan is powering on at 100% by itself when heating begins, or sometimes when the bed reaches 50° or so...
It goes on during the auto leveling process.


It shuts down when the printing begins as I have a M107 command on my startup script, but then it get back to 100% during first layer (where it should be off). Starting at the second layer, it stays at 40% power as it should.

I could not find any good reason for this behavior in the configuration.h file.

Any idea ?

Thanks !

It appears that your Configuration files are setup correctly.

What setting do you have on your slicer program.

I'm using Simplify3D just like i did before Marlin (didnt have that issue at the time) with 0% power for first layer and 40% power starting at layer 2.

Thanks

Hi,

With some more testing i can confirm that heating the bed if powering on the fan. Heating the hotend alone does not.

Make sure that none of the tabs on the RAMPS MOSFETs are touching each other. If they do when one MOSFET activates the touching MOSFET will also activate. I had this problem with almost exactly the same symptoms you're experiencing and I've seen at least two other people with the same problem - just bending the MOSFETs to ensure that they do not touch each other should solve this issue.

EDIT: Actually, my symptom was the opposite - whenever the fan turned on the heatbed would also turn on. But the solution is the same.

Edited 2 time(s). Last edit at 05/22/2018 02:52PM by MMcLure.

Quote
MMcLure
Make sure that none of the tabs on the RAMPS MOSFETs are touching each other. If they do when one MOSFET activated the touching MOSFET will also activate. I had this problem with almost exactly the same symptoms you're experiencing and I've seen at least two other people with the same problem - just bending the MOSFETs to ensure that they do not touch each other should solve this issue.

EDIT: Actually, my symptom was the opposite - whenever the fan turned on the heatbed would also turn on. But the solution is the same.

Hi there,

Indeed the three of them were touching each other... Silly me not to pay attention du that during the wiring part...

And Kudos to you since a first test i just did tends to show that the issue is resolved. I'll try again in a few days when the printer is fully reassembled again (waiting for a new hotend) and confirm then.

Thanks

Quote
MMcLure
Make sure that none of the tabs on the RAMPS MOSFETs are touching each other. If they do when one MOSFET activates the touching MOSFET will also activate.

This is one reason I installed an aluminum Heat Sink Bar with insulator kits. (I have a different Board but still similar.




Edited 3 time(s). Last edit at 05/22/2018 05:28PM by Roberts_Clif.