temp sensor on extruder follows bed temp when extruder heater off

I'm building a rep rap and can't seem to get temp settings right for the life of me.

I now have two honeywell thermistors (one for bed, one for extruder)

at room temp the bed reads 20C and the Extruder reads 30C-this doesn't make sense since they are the same sensor type and were selected properly in the configurator.

i commanded extruder to 40C and bed to 30C and i read ~80C on the extruder and 30C on the bed as measured by a fluke thermocouple readout.

I then decided to turn off the bed and waited till it went back to room temp.  bed cooled to room temp as indicated by both thermocouple and repetier host software. Extruder remained reporting ~40C and measured ~80C via thermocouple

I then decided to turn the bed back on to a temp higher than the extruder and commanded 50C to the bed.  As bed temp increased the extruder temp also started to increase as reported by the repetier host software but remained ~80C as measured by thermocouple.  The graph on repetier shows extruder temp at ~55C with bed temp at 50C and the graphs are parallel.

any ideas?  Please help


  • then I bumped the extruder to 70 C and read about 140C with the TC when the software showed 70C.

    I then turned off extruder heater and watched the temp come down to ambient via the TC.  However on Repetier it only came down to ~53C (bed is at 50C)
  • There is surely something wrong. First honeywell produces more then 1 thermistor, so make sure your setting matches the one you have.

    You also use the term thermocouple, which is something different then thermistor. You can not put a thermistor in a thermocouple pin and not a thermistor into a thermocouple pin. Well you can, but the result will be not what you expect.

    So check what you really have and where you connected it.
  • I used a thermocouple with an independent thermocouple readout (Fluke 714) to check the reported temperature with the actual temp since I burned up a heater already.  I've also now melted down my J head and am buying a new one.

    I purchased my thermistors from a local 3D printing company and they told me it was option 7 in Marlin.  I looked up option 7 in Marlin and it is the same honeywell themistor which I selected in Repetier.

    Can you speak to the tracking issue?  Why would the readout on one thermistor follow the other when it's not actually reading that temperature?   Is my ADC possibly fried? Some kind of weird crosstalk? This is mind boggling to me and appears that it would be firmware related.  I have checked the ADC with a potentiometer previously.  Is there a way to report the ADC value in Repetier?  I had previously tried Marlin and had found a  line that I uncommented which wrote the ADC value to the Serial monitor when running the M105 command, but I haven't been able to locate a similar line in Repetier.

    I agree that surely something is wrong I just have no idea what it could be at this point.  Please help me with troubleshooting suggestions...I'm at a loss at this point.  I have spent weeks at this point dealing with temperature issues.

    Please help
  • Weeks? Ive had my 3D printer since February and I still havent seen any software or combination of settings heat the hotend and drive the motor for the Extruder though I have just once seen that rotating using Replicatr G. I can get my heated bed to warm up - right now it's doing a very nice job of keeping my coffee warm so at least that's something though $500 for a coffee warmer is a little steep if youre not a Euromillions Jackpot winner, or an unpaid one ;) 2 Feedback comments on the Heacent 3DP02 both buyers said their machines were mismatched to the software and also several parts in the kit. As was mine. Hopefully this isnt just a case of a bunch of ***ts intercepting products in transit and replacing with faked CDs in order to take control of all "Tech Support" because my WIndows 7 Original DIsc WAS intercepted in the mail and stolen from an Oldham Sorting Office according to the paper trail. Ive wondered for a while now if this isnt the true blackmailing backlash of "Open Source Programming" - that one set of talented people write code that another set gets hold of and sabotages so they can charge cash for repairing what they damaged in the first place. Don't like to be that cynical but all the evidence seems to be pointing that way. Youre not JUST paying for the machine/software, youre now paying internet "tech" blackmailers.
  • My printer is a ground up build so I don't have anyone to call for tech support.

    At this point if I knew someone willing to provide support, I'd probably be willing to pay.  I hope what you say is not true and that someone can help me.
  • You can send M105 X0 and then you get raw adc values. Not sure when this feature was added, but 0.92 hat it and most probably 0.91 as well.

    You can also measure your thermistor value resistance with a multimeter. At 25°C it should be 100K and if it heats up resistance should go down. And as I already told make sure to use the thermistor inputs and not the thermocouple inputs!
Sign In or Register to comment.