# A4988 driver cooling specifications

When exchanging the mainboard of my Ultimaker Original, I found the new (unoriginal) mainboard to have a condensator that is quite a little higher than on the original, which means the fan duct doesn't fit any more.

I read somewhere that those A4988 stepper motor drivers don't have to be actively cooled, but a heatsink will be sufficient:

After testing the theory I found the heatsinks to be really hot, but not too hot to touch. Sadly I do not have any means of temperature measurement other than my fingers...

How hot do they normally get, when should I abort printing and look for a different solution?

Are there any good solutions other than the original cooler & cooling duct?

• Adjust the current according your motor; an excesive current will heat the driver and also the motor. – Fernando Baltazar Sep 8 '18 at 7:49

A4988 become hot when a lot of current draw from them . If it is more than 1.5 Amp. Also you will notice missing steps, missing layers, abnormal print and Stepper motor become hot .It automatically shutdown at max temp.

• That does not really answer my question, given that I didn't change the settings of my printer. – Markus Appel Sep 7 '18 at 14:42
• What should I do about high current draw? Can I run the drivers without active cooling as long as they behave normally without risking destruction? – Markus Appel Sep 7 '18 at 14:44
• It is good to add active cooling. It also depends on your ambient temperature. My advice you to check stepper motor temperature for high current draw. Because stepper motor become hot on high current draw. – Himanshu Sep 7 '18 at 14:54
• They do get hot, but they always did. Do I need to fix this? – Markus Appel Sep 7 '18 at 15:14
• Not in my opinion – Himanshu Sep 7 '18 at 15:20

The answer to that question is not as simple as it looks as we don't see the hardware. Main issue is the current pointed by Himanshu, that generates most of the temperature in the silicon chip.

I was using drivers without active cooling, but my case was open so there was enough heat dispersion.

You could do a dry run - by creating a command file with G-code like below

G28
G1 X200 Y200 F6000
G1 X0 Y0 G1 X200 Y200
...
... copy and paste many times to have a 10 minutes run on the printer


That will keep the stepper busy and you could observe radiator temperature and probably see/hear miss-steps.

other solution could be a duct like this one