1

Hello,

I am in the process of calibrating my first own sourced printer. The bed heats up to 90C on its own(without my command) and refuses to cool down. It is an mk3 alu bed with 12V supplied under load and the bed is only drawing 10.5V. Could someone help me ?

Thanks

2

Custom firmware or stock? What type of control board? Where is the bed heater wired to?

3

The bed is not “only” drawing 10.5v… the controler send eighter 12v or 0v. on a on-off cycle. After wires losses it is normal to get only 10.5v at the bed terminal. so basicaly your bed is alway at full ON 90oc is a typical temps for a controler stuck at always on. Could be a wiring issue. or mosfet on your controler stuck ON.

4

Marlin firmware, ramps 1.4, bed heater wired to d8 of ramps board

5

Oddly, it sounds like a bad ramps board. If you are on d8 with Marlin the symptom should not be possible. Can you attach your configuration.h and pins.h?