HeatBed shuts down after 70ºC

Hello

I've got a Prusa i2 with a 30A 12V power supply and i've been printing with PLA for a couple of weeks without a problem, but last night i tryed printing with ABS for the first time. I ajusted the bed to reach 105ºC wish she took a long time to reach, but today when i wanted to do the same or just setting it manually to 80ºC the bed just gets to around 70ºC and then just cooldowns without warming up again. The led on the Ramps 1.4 lights on when the is warming but then after she reachs the 70ºC just turns off and dont come on again.

Can anyone help me please.
Thanks

A few minutes ago i manually set the heatbed just to 50ºC but when he got to about 40ºC it just shut down and won't warm up again. May it be from the termistor?

It could be the yellow polyfuse switching off (the larger of the two). Try aiming a fan at it.

---

_______________________________________
Waitaki 3D Printer

A voltmeter is your friend with problems like this. A cheap one will do just fine in this case. Check your power supply voltage, voltage at the 11A connector on the Ramps (or what ever) board. Check the voltage at the heated. That should help you figure out where things are running out of power.

If it's a polyfuse popping, check for things like shorts at the heatbead mounts. Black burn marks are often a good clue.