Short circuit error on Kossel XL with duet wifi



  • Hello all,

    I'm receiving the error message "temperature reading fault on heater 1: open circuit". I replaced the fuse with a .25 amp fast acting fuse and 5 x 20 fuse holder, but that didn't work. I made sure to solder the fuse to the same spot user "cap" did in this thread: https://www.duet3d.com/forum/thread.php?id=247. This is on my new kossel XL with the duet wifi. Everything was working fine until i replaced one of my fans on my hotend. I accidentally had it wired wrong and it burnt out the fan. Though the hot end was still heating up fine. It wasn't until i got the new fan, replaced it, that i started to get the above error message. When i checked my hotend for a short i indeed saw that the back of my z sensor board was touching the hotend. Fixing that and the fuse i assumed would be the end of it but the message remains. Even after resetting the hotend in the duet web control with command M562 P1.

    thoughts?


  • administrators

    Is the bed temperature reading normally, assuming you have a bed heater? If so then the VSSA fuse is OK.

    I suggest you use a multimeter to check that the thermistor is not shorted to the hot end metalwork, the hot end heater, fan wiring, or anything else on the hot end. Then try plugging it into the E1 thermistor connector, and see if you get a temperature reading for heater 2.

    HTH David



  • Thanks for the reply, forgive my ignorance but how can i go about checking for a short with a multimeter?



  • measure resistance between both parts which could be shorted, if there is a near zero resistance it is probably a short.


  • administrators

    Also to expand on that make sure the thermistor and heater connections are unplugged when you are measuring.

    There are many articles you can google and youtube videos on how to use use a multimeter to test for shorts between wires.



  • Ok, so i started measuring resistance between different points.

    Measuring Thermistor the readings jump around quite a bit.

    I did however measure the resistance of my heated bed from the two red wires and it was .000. Is it possible my bed is the culprit?


  • administrators

    Can you describe how the thermistor values are jumping about. What values do you get and do they change when everything is still or only when you move/touch the hotend/bed

    0 Ohms on the heated bed indicates a short circuit. I would expect about 1Ohm for a "standard" heatbeds on a 12V system



  • @T3P3Tony:

    Can you describe how the thermistor values are jumping about. What values do you get and do they change when everything is still or only when you move/touch the hotend/bed

    0 Ohms on the heated bed indicates a short circuit. I would expect about 1Ohm for a "standard" heatbeds on a 12V system

    I'll have to record all of the readings i get from the thermistor but i made sure to be steady and accurate with it. If this heat bed is indeed shorted, what would the next step be? Replacement? Thanks for your help so far.


  • administrators

    One more question, are you taking the measurements with the heatbed/ thermistors unplugged from the Duet board? If not you need to.



  • Thermistor values on the hot end jump around from .338, .466, 1.326, and about 10 other numbers. The measurements of resistance were taken from the heat bed while it was completely removed from the printer.



  • The interesting part is that even though the heat bed has a short it heats up just fine, it's the hot end that doesn't heat up. What else can i check for to diagnose the hot end issue?


  • administrators

    Those thermistor values are so low - looks like the multimeter just picking up noise. You are looking for values in the region of 100K for a 100K thermistor.

    Do you get the same readings of for the extruder and bed thermistors?

    If not then what temperature for the bed is displayed when the bed thermistor is plugged in?



  • @T3P3Tony:

    Those thermistor values are so low - looks like the multimeter just picking up noise. You are looking for values in the region of 100K for a 100K thermistor.

    Do you get the same readings of for the extruder and bed thermistors?

    If not then what temperature for the bed is displayed when the bed thermistor is plugged in?

    I'm not sure how to test the extruder thermistor, there's only a white connector with 4 different color wires coming out of my extruder. ( E3D Titan ).

    When my bed is plugged in and reading from the duet wifi control, the temperature is 34 Degrees Celsius.

    Thinking maybe my hotend board might be burnt out?



  • There is no extruder thermistor. There is the hotend thermistor.
    The 4 color wires from Titan are the motor wires. You need to measure the two wires (either white or red/black) coming from down below, inside the heater block where the nozzle is.



  • @sigxcpu:

    There is no extruder thermistor. There is the hotend thermistor.
    The 4 color wires from Titan are the motor wires. You need to measure the two wires (either white or red/black) coming from down below, inside the heater block where the nozzle is.

    Gotchya, measuring those 2 wires from my hot end i got a range of numbers. I listed a few of the ones in an above post.


  • administrators

    So just to be clear you should have 2 thin wires and two thick wires coming from your hotend. Then another 4 wires (probably black blue green red) coming from the e3d titan motor. Ignore the 4 wires coming from the titan motor. Check the resistance across the two thin thermistor wires where they plug into the board, but with them not plugged into the board. If you get similar readings to those you already mentioned then you have a short circuit on your thermistor



  • @T3P3Tony:

    So just to be clear you should have 2 thin wires and two thick wires coming from your hotend. Then another 4 wires (probably black blue green red) coming from the e3d titan motor. Ignore the 4 wires coming from the titan motor. Check the resistance across the two thin thermistor wires where they plug into the board, but with them not plugged into the board. If you get similar readings to those you already mentioned then you have a short circuit on your thermistor

    Ok so the 2 thick wires are what i originally tested and what gave me the numbers that jump around.

    The 2 thin wires i'm not able to test because of the connector they go to, i tried sticking my multimeter sticks in the 2 holes but didn't get a reading. Should i cut the wires off from the connector to get a reading from the bare wires?

    I've attached a picture just to show what i'm talking about.

    https://postimg.org/image/dqe59walv/


  • administrators

    You could put wires in the connector holes and measure between those.



  • @dc42:

    You could put wires in the connector holes and measure between those.

    I put wires into the holes as far back as i could and measured but still get a reading of .0L. Perhaps i'm measuring it incorrectly? I used speaker wire and made sure to stick them in as far as they would go.



  • I ended up stripping the wires just to be sure. Still same error message.


 

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