Hotbed overheating

[Brmatt]

Having some trouble with the hotbed overheating. After various heater tunings and parameter updates I have had no success. The main issue is when I set the target temperature for the bed it will reach and then exceed that temperature, triggering the fail safe. Here is my current parameters:

[dc42]

I presume those M307 values came from tuning the bed. If they are correct, your bed heater is more than twice as powerful as it should be. Are you sure you are not running a 12V heater on a 24V supply?

If those M307 values are in config.g, check that they are not being overridden by a different set of M307 parameters in config-override.g.

If you want to continue using that bed heater, for safety reasons you should definitely use a thermal cutout to reduce the risk of fire. You should get less overshoot if you restrict the PWM to about 0.4 in the M307 command.