motors getting really hot!!

I am using a geared nema 17 for my bowden extruder (1.75mm) and it gets really hot. What current should this motor be set at in the repetier firmware?
RAMBO board (135= ~0.75A, 185= ~1A)
Currently they're at {150,150,150,155,0} which was already lowered from {175,175,175,185,0}




Edited 3 time(s). Last edit at 02/09/2014 02:48AM by Ketchup.

What does it mean really hot? How long is your stepper without shaft?
I push about 1.3A to the extruder stepper and it is not getting hot. It is only about 45°C. Its phase resistance is 2Ω. That means thermal load from one phase winding of about 3.4W. The stepper does not have a heatsink nor is it actively cooled.

Your stepper has thermal load from one phase winding only. 2.8W (when run at 1A). The magnetic components of your motor would need to be really crapy to lead to really high temperatures at 1A.

Yor motor has maximum temperature of 110°C. If it is mounted to ABS do not mind if it goes up to 80°C. If it is mounted to PLA do not mind if it goes up to 60°C.