Quote Originally Posted by PhilippG View Post
Thank you joop.
I may try it, too.

I have discovered another "problem" and was wandering, if that behavior is correct.

My method was printing a gcode file with just one line of code and then measuring the voltage on D8 and D9 first with the devices disconnected, then with the devices connected.
When the printer starts, both are at 0V.
Every measurement was done directly after switching on the printer.

Unconnected:
M106 S255 (Fan fully on) -> D8 = 12V | D9 = 9V
M190 S110.00000 -> D8 = 0V | D9 = 0V

Connected:
M106 S255 (Fan fully on) -> D8 = 2.7V | D9 = 0V
M190 S110.00000 -> D8 = 0V | D9 = 0V


Summary:
M190, instead of heating the bed, does nothing, but the Fan-Speed controls the heating of the bed.

Is it supposed to work that way or is there something seriously broken?
I think you have your hot bed and fan connected backwards. D9 is connected to the fans. D8 to the hotbed.