Left thermistor readings are intermittent

[swoop_ds]

I've been getting the "Temp readings are failing, check wiring" error message for my left extruder. The wierd thing is that it only happens intermittently, but regularily (as in I can barely get a print started). Wouldn't a damaged thermistor just not output readings at all? What would cause it to kinda flick on and off a lot?

[Mjolinor]

Your wiring is suspect. Thermistors rarely go intermittent within themselves but it is not unheard of. At less that a pound each just replace it.

[ARosch]

Sorry to bring this old thread back up, but I am having the same problem. I was in the middle of a print using only the right extruder and got the error tone and a message saying that my left extruder temperature readings were failing.

Is there a way to find out if it is just the thermocouple failing without buying a replacement? I measured the resistance between the terminals of each thermocouple at the control board, one was 16M ohms (so basically open circuit) and the other was 4 ohms.

This is what I would buy as a replacement: http://www.makergeeks.com/du3dprth.html

[richardphat]

I dont have a forge, but on my delta, if a temperature sensor fail, it would write something like -10C right when the printer is powered.
Maybe it would help you?

[ARosch]

I dont have a forge, but on my delta, if a temperature sensor fail, it would write something like -10C right when the printer is powered.
Maybe it would help you?

The left sensor always reads 24C immediately after turning on, before it gives the error. I have tried heating up the nozzle with a heat gun before turning it on, and it always says 24C. Perhaps 24C is the default value? The other extruder doesn't read 24C when turned on, it reads the actual temperature.

[AussiePhil]

I had this exact issue a week ago, turned out to be the wire had broken right were it is zip tied to the top of the print heads. the thermistor wiring is stupidly solid copper and subject to fatigue fracturing at any point that bends the wire backwards and forwards.
on mine only the red wire had fractured/broken.

[ARosch]

I had this exact issue a week ago, turned out to be the wire had broken right were it is zip tied to the top of the print heads. the thermistor wiring is stupidly solid copper and subject to fatigue fracturing at any point that bends the wire backwards and forwards.
on mine only the red wire had fractured/broken.

So did you just replace the entire thermocouple?

[Mjolinor]

Thermistors and thermocouples are not the same thing.

[ARosch]

Thermistors and thermocouples are not the same thing.

Mine is a thermocouple, and I kinda just assumed that all the other people meant to say thermocouple.

[AussiePhil]

Mine is a thermocouple, and I kinda just assumed that all the other people meant to say thermocouple.

I meant the thing that measures the temperature of the head......................... think we all knew what we meant.

To answer your question, No I just soldered the wire back together where it had broken, put a layer of heat shrink over the top of the join and carefully put all the wires back in the bundle wrapping stuff.
To find the break I had to pull the entire length of wiring out of the bundle so it is likely easier just to replace it if you have the time to order the replacement.

Considering the wire itself is a single solid strand I consider this a poor choice due to the movement of the head(s) and Flashforge really should consider either shipping a spare or sourcing units that use multistrand wire.