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My Rostock Max v2 was purchased used, even so I am learning a lot. I decided to hook up a 24 volt power supply to power my heated bed. I am using the out put from the control board (originally to the bed) from Rambo to control a solid state relay. To test this I used the lcd control panel turn the bed on and off. So far so good. The problem I am having is auto tuning the bed. When issuing the command to auto tune the hot end starts to warm up. I am issuing the following command "M303 E2 S90" I assume E2 because that is where the power is coming from to switch the relay (Heat Bed 2 as the board indicates). The instruction manual describes the procedure to auto tune the hot end (the command is "M303 S200", as I understand when the "E" is left out extruder 0 is assumed) I have tried googling for help but no luck. Could it be that I need to change something in the eeprom with Matter Control. I have never tried to auto tune the heat bed before but was successful at auto tuning the hot end. Can someone here please help

Thanks again for your help.

The autotune for the bed is a different command.

And from ehat i remeber does not have an E in it.

Download the rostock max v2 manual. And search for autotune.

Thank you for the quick response. Thru further research I discovered that I should have been using the letter "P" to address the heated bed. Thus giving the command "M303 P2" to direct the control to auto tune the heat bed. Still not sure why when giving a command to a non existent extruder the one on the machine starts to warm up. Oh well...one step closer to success.

Thanks again.