Problem with Hot End v4 Thermistor.

[Metalrat]

Hello All,

I am hoping someone can help me with advice. I have a Felix V2.0 that I have had for about 9 months now, but I have not done a lot of printing with it due to issues I have learning and replacing hardware.

My printer has not had a good life, it came to me damaged from the supplier, it looked like someone had dropped it and had a very heavy weight on top as the top bar with the handle had been pushed down 5cm on one end. (I am certain the problem was not with Felix direct, Mr Feliksdal has always offered the best of support and I am sure this happened locally here in Australia).

The first 6 months I spent working on it (a couple of posts here with problems and people helped me out, again I say thank you). Just before Christmas 2013 I decided to upgrade the print head from the v3 it came with to the v4 because of issues I was having with the v3 (It turned out to be clogged with a bit of plastic that had turned almost to glass).

I bought the v4 and a spare thermistor as well as a spare heating element direct from Felix printers and they arrived here a week later and I was very happy.

It took me a couple of weeks to get the time to be able to change the print head but when I did I spent the night trying to print again, which I had not been able to do for a month and I was happy despite the quality of my prints (still working on how to stop the bottom layer lifting in places and warping at times, but I think this is user issues and just a learning experience). That night I turned the printer off and went to bed looking forward to the next day. But when I tried it again the repetier host software told me that the hot end was at 0 degrees and I was puzzled.

I played with the wires a little (just fiddled them) and the temp would go up and down and behave strangely.. So I sighed and thought well at least I have a spare but I had no time to install it that day after playing a bit. It turns out I had no time for most of 2 months due to issues with work and such.

Well yesterday I put the replacement thermistor in and again I got to print a bit, I made the other half of the spool holder spindle that I wanted and was again happy.. But... I get up today and turn the printer back on, and again the repetier software is telling me that the print head is at 0 degrees. I tried just fiddling the wires but no good. I turned the printer off and connected the old thermistor again and it worked the way it had before.. ie if I wiggled the wires I got some readings.. so I connected the replacement again but no temperature was shown (ie 0 degrees).


That is the long story, simple version.

• New print head goes in, works for one day then next day thermistor is not working properly.
• Put in new thermistor and works for one day then next day thermistor is not working properly.
• Type of print head is V4.
• Printer is Felix v2.
• Repetier software says no updates available I am using the latest version.
• I am trying to print via USB cable from my PC.
• Thermistors bought from Felix, they have the long white leads.

Can anyone offer suggestions or advice? I will of course order new Thermistors but this doesn't sound like it will necessarily work as either I am doing something wrong or there is a problem here.

[Dreide]

I doubt that the thermistors are the problem, but measure their resistance when disconnected. At room temp they should have around 100kOhm. This should not change when you fiddle the wires. If it does, try to locate where the lose contacts are; is it directly at the metal can or is it where the wire extension is attached?

Besides that, carefully inspect the electronics board, especially the area close to where you connect the thermistor. Use a magnifier and look out for metallic debris potentially causing short circuits. Also look out for bad soldering.

[Metalrat]

I've checked the electronics board and can find no bad solder or dry joints or debris and such.

I've measured the resistance of the thermistor that if wiggled would give results (at the metal container end) and it would appear to be 1.018 M Ohm.. not K but M..

I'm trying to source some local thermistors apparently RS electronics has them and I will try them out. Right now I have nightmares about needing a new electronics board, soon I will have had to replace almost all of it and I hope at least by the time I have the issues go away

[Dreide]

I don't know. What you are telling here does not make a whole lot of sense. You were talking about a weird intermittent printing (or non-printing) behavior which appeared the same with two different thermistors. If it was really due to the thermistors, both thermistors would have to have the same intermittent defect - really very unlikely. Now you measured only one thermistor? How can you measure "at the metal container end" anyway, or did you just mean you applied the "wiggling" at that end? What resistance do you measure when you don't wiggle? If the wiggling makes a difference then you should be able to locate the slack point. Note that at 1MOhm, you might get different readings just by touching the stripped cable ends. They are stripped, right!?
Do you measure the same with the second thermistor?

[felix GH]

I had the same problem and yes both had the same intermitting defect after printing at 215C+.
The defective thermistor read at 24C in the Mohms the spare one 95Kohm at 24C and after the 2nd one went bad it was also into the Mohm range.