Heat Bed heating up when i turn power on

I’m not sure if this problem has come across anyone else but I’ve tried to find it and i can’t. For some reason once i turn on the power to my smoothieboard v1 the heat bed starts to heat up for no reason. there was no problem before and i haven’t changed anything in the config for over a year. Does anyone have any idea why is this happening? Please help

Does it turn on full power without temperature regulation, or does it turn on trying to stay at a given temperature, if so what does M105 say? Does this go on forever, or stop after a while?
This is super odd. Make sure you are using both the very latest firmware, and the very latest config file example.

Like i said before i haven’t done anything with my config file or software for almost a year and everything was working fine. That happens at the same time i turn on the machine no matter what i do it just keeps heating up, even if i set up temperature to 50 it still goes higher and higher and it doesn’t stop at all.

Since it sounds like you are saying that the smoothie is measuring the temperature correctly, it sounds to me like the bed switch has failed. MOSFET or SSR?

How can i check that and if so is that mean i can throw the smoothie away or maybe i can use a external MOSFET instead?

If your mosfet is failing always on ( a video of the problem with leds visible would help here ), then yes you can use an external mosfet or SSR to solve the issue, indeed.

Ok so here is a video of the board from start. I noticed also that when i disconnect the heat bed from the board the mosfet doesn’t light up anymore. can there be also a problem with the bed itself? Also I’m sure this has been asked on the forum but since we are here already how would i connect the external mosfet? would i have to use different pin on the board?

Also config part for hotend