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 &amp; cooling duct?
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.