I seem to be having temperature issues all of a sudden. I'd been printing the past couple of days without any problem. I have an He3d RepRap Prusa i3, with a E3d v6 hotend. I'm using Repiter to control the printer.
The last print I tried to do, I noticed some oddities. The temperature of the hot end did not reach temperature. It was set to 175 and it reached 168, or something like that. I had the heat bed set to lower then room temperature cause I didn't need it on. I noticed that the temp reading for the heat bed was jumping around. I turned everything off, disconnected, and went to eat dinner. When I came back, and reconnedted, I had an ERR:MINTEMP on my lcd screen of the printer. I checked the leads for the thermisotrs and they both checked out fine. After a few resets of the Ramps board, the error went away, but the temp readings for the hot end and the heat bed are all over the place. I took a screen shot of the temperature curve. The really odd part is, they aren't switched on. I really have no idea of how this came about.

make sure the thermistor is secure and the heater element is tight in the block, I used high temp silicone to hold my thermistor in even try another thermistor

buy a 6 pack of those thermistors, they are cheap and break easily (at-least i break them all the time). I have also had to buy a replacement heater cartridge for a similar problem, but try replacing the thermistor first.

I did find the solution. The problem was in the servo for the auto level sensor arm. The servo went on my. When I disconnected it, the problem went away. I now have a new servo and everything is working fine. Now my issue is getting Marlin to flash to the board. It was working after the correction, then it wouldn't flash although Arduino would say it had, and now Arduino just gives me errors when I try to compile the sketch.