Preheat Error after working for several reels
Hi folks,
Built a new Prusa Mk3 and it's working fine (apart from a z-axis issue that Prusa are sending a replacement nut for)
It's been printing fine for required models for the last couple of weeks (maybe two reels of 1kg filament work) - however it's just started with intermittent preheat errors.
I've read the forums on this and it appears to be a thermistor fault if I'm reading correctly - ie the temp reading are showing as zero on the LCD screen, ie:
Preheat Error
215C/0C
60C/0C
Now I've found by fiddling around with the two sets of wires going into the hotend (the thicker red wire pair and the thin blue ones), this fixes randomly and I can print again. However it tends to come back after a while.
Do I need to replace the hotend to get this working or is there any other tests I could try?
Re: Preheat Error after working for several reels
Check the entirety of the thin cable. That's the temperature probe.
Verify the wire isn't stretched taught by the zip ties at the back of the extruder. You may need to re-zip tie the heater block wires leaving a little bit of slack.
Check the other end of the cable inside the EINSY case. That end may have pulled free of its plug. Mine had been overstressed by the yellow/green shrink wrap to the point of one wire pulling out of its crimp connection inside its plug. Worked fine for a few weeks, then stress by the shrink wrap levered out the wire. You'll see that the shrink wrap is long enough to be deflected when the EINSY cover is closed. If the shrink wrap was applied too close to the plug, it's a failure waiting to happen.
Re: Preheat Error after working for several reels
Hmm, check the wire appears to be fine - tried reseating in the einsy board - no obvious problems there.
Also added a bit more slack (didn't appear over tight at the extruder end either)
Still same error - appears to be more consistent now - Bed is heating up, just not the extruder.
Any other checks or tests?
Re: Preheat Error after working for several reels
Ah spotted it I think.
Scraped away some of the white surround on the thermistor end and can see one of the sheaths is bare, so suspect this wire is loose.
Bit surprising on a two week old build, but nonetheless, keen to get working before Christmas!
I've ordered replacements from Prusa - but not sure how quick their shipping is, so may order extras from e3d as feels like this is a fairly weak part of the design anyway.
I assume this is the right replacement? (Prusa hyperlink to this in their replacement guide)
https://e3d-online.com/thermistor-cartridge
Just one question, the cable here looks pretty short? Would this reach or is the picture inaccurate
Re: Preheat Error after working for several reels
Is the temperature still reading 0?
If so, there is a complete break in the thermo sensor cable or the thermalcouple is completely dead.
If it changes between 0 and some other number when you wiggle the cable, the break is intermittent.
A partial break inside the plug body due to the wire starting to pull out of its crimp won't be visible until it's really broken free.
[EDIT]
The e3d sensor cable is too short, but they include a molex cable. You plug the sensor into the longer molex cable and that reaches the EINSY.
[/EDIT]
A multimeter could pretty quickly test continuity of the wiring. I'd want to verify the plug crimps are OK before ordering a new sensor.
Re: Preheat Error after working for several reels
Ah perfect, sounds like I could use the molex approach then. Have to say cable is pretty feeble, so like to get something better quality to replace.
Yes, consistently reading 0 now.
Just need to work out how to get the cartridge out the block as it's jammed in even with the allen screw removed - might need to heat up the block somehow....
Re: Preheat Error after working for several reels
If you know someone with a multimeter, have them do a quick check of the cable. It might save you the hassle of doing an entire thermocouple replacement. They can put a pair of needles into the disconnected plug and check continuity from each needle to the other end of the cable (at the sensor). It may still be a hidden fault inside the plug. If that's the case, it's a lot easier fix.