Problems with temperature reading

Hello,
I tried using my printer recently, and when I went to heat up the extruder, the temperature reading would just drop out of nowhere.




I switched both of the thermistors to see if that was the problem, and the other thermistor acted the same way, so it's not that. It's somewhere on the board, or its a software issue. I'm using RAMPS 1.4 with the sprinter firmware, and I'm using pronterface to control it.

If anyone has any idea what is wrong, it would be greatly appreciated.

Have you checked the thermistor reading at the Ramps socket - should be around 100k for a 100k thermistor at room temp

Does the temperature rise and fall? I had a problem where the wire connection to the thermistor fatigued from constant going back and forth until it eventually failed. It would make connection with the carriage in certain positions and break connection in other positions.

I ran my printer without any filament in it, as to not damage the hot end by having the hobbed bolt force filament into it. The heat bed acted normally. The temperature reading on the hot end, after plummeting when turning it on, and after I started the print, it leveled out at 35-40 degrees C.

Could it be the heater resistor in my hot end failing?