Extruder temp extreme fluxtuation while printing

[Shizuma]

So I noticed last night when I was printing that the extruder temp was fluctuating wildly while printing, well beyond being able to be the accurate temp, while heating up it's perfectly fine and reads a consistent temp, but once it started printing it would go from 232 to 59, to 203, to 127, etc, just bouncing all over the place, it still seemed to be printing perfectly fine but I stopped the printer out of fear that the false temps would cause the hot end to heat up too much and melt the peak . Does anyone know what could cause the temps to bounce around like that when print? my only thought was a bad thermistor, but then it shouldn't work fine when heating up, would a loose wire to the thermistor cause that?

[guanu]

that large of a variation I would say either a loose wire (or cold solder joint to the leg of the thermistor)... also make sure the thermistor is seated in the hole of the heating block good... but I would say loose wire or cold solder joint...

Guanu

[Shizuma]

The thermistor should be seated properly, it was RTV'ed in place and then I wrapped the hotend with kapton tape, so I can't imagine it could have worked itself out, I'll check the solder joint and wires to see if I can spot the cause of the problem, if not then maybe this is the printers way of saying time to upgrade to the E3D hotend.

[dtgriscom]

I'd be really careful about this; if your thermistor (or its wiring) is flakey then it's very possible to totally roast your hotend and PEEK.

[Eaglezsoar]

The way it remains steady when the printer is not moving then acts up while printing (movement) does indeed indicate a loose wire with the thermistor or a remote possibility of heater wires to the hotend.