V3 Bed only Heats while Hot End is active

[tehwadeski]

Hello, been wrestling with my heated bed on my Rostock Max V3 for the past few weeks. For some background, my heated bed appears to only heat while the hot end is active. Is this by design?

Going through the LCD menu I choose >> Adjust Temps >> Bed Temp >> Set to anything, let's choose 50C.
The bed set point updates to 50C, but nothing happens.

I go back to the LCD menu >> Adjust Temps >> NOZ Temp >> Set to anything, let's say 150C. I turn the knob, the indicator rolls from 0 to 100C (my minimum temp) and then I continue scrolling to 150C and set that. The INSTANT the LCD screen rolls from 0 to 100C, my heated bed LED lights up and the bed begins heating.

What is interesting is the Nozzle will heat up to the desired target and sit there, in this case 150C. The bed will continue to heat, almost into a runaway state while the nozzle is hot. Further, if I were to set the NOZ temp to 150C and leave the bed temp at 0, the bed would still heat and continue in a runaway fashion.

There seems to be a strange interlock between the bed and the hot end. My bed will not heat without the hot end active, but then it's on and on all the way.

I apologize if this topic has been discussed before.

[tehwadeski]

As a follow up, if I set the hot end to 150 the bed will begin heating. If I catch the bed at around 45 - 50 C and start printing, the runaway condition is less likely to occur. Is there a difference in heating commands when I set the temp via LCD or if I set the temp in my Gcode?

Thanks.

[pouncingiguana]

This almost sounds like a wiring issue. Is this a new problem, or has the printer always done this? It kinda sounds like your bed is wired to your hot end.