<p>So, the problem is in fact of a hardware nature. By replacing RAMPS 1.4, the problem went away.</p>
<p>Arduino, firmware, G-code... everything is the same, only RAMPS was replaced.</p>
<p>I'm going to find a suitable MOSFET replacement.</p>

CC BY-SA 4.0
2021-07-16T22:49:48.560Z
2021-07-17T00:46:35.210Z
2021-07-17T00:46:35.210Z
HerGiz
<p>Sounds like you have a short in your sensor or sensor circuitry.  However, if this is the case the sensed temperature is higher than the actual hotend temperature.  Does your hot end go cold when the sensed temperature takes off?  A short could also show the hotend temperature going up at an unrealistically fast rate.  This doesn't seem to be your case.</p>

CC BY-SA 4.0
2021-07-14T15:21:00.597Z
No. When temperature goes up, so is nozzle shoveling, and after error is detected, I have to wait for the head to cool of to be able to lit Z axes it leaves a big hole around nozzle...
HerGiz
CC BY-SA 4.0
2021-07-14T14:59:05.940Z
2021-07-14T15:54:39.580Z
2021-07-14T15:54:39.580Z
Perry Webb
<p>I have a &quot;classic&quot; home built 3D printer, Arduino Mega, RAMPS 1.4 with Marlin 2.0.</p>
<p>It worked, was put in storage, and now I am trying to get it running again.</p>
<p>During all of the testing phases, the PID autotune, etc., the temperature of the hotend is stable.</p>
<p>When printing, for a few layers (4-5), the temperature is OK, despite the part fan coming on and off. However, after 3-4 mm of printing the temperature just rises and rises and rises, and after 275 °C thermal protection kicks in...</p>
<p>MOSFETs have additional cooling and a fan over them.</p>
<p>I'm out of ideas... Help!!!</p>
<p>My config files and G-code are <a href="https://github.com/hergiz/singles" rel="nofollow noreferrer">here</a></p>
<p>Using PrusaSlicer.</p>
<p>Why do I see a temperature rise on the display? Last time I unplugged the printer and left it on USB power then gave it power again. During USB power temperature was steadily going down, as soon I plugged the main cable it resumed printing and the temperature rising again.</p>
<p>I did another test. 20mm above bed started printing, and got same result. I captured on video entire process <a href="https://www.youtube.com/watch?v=5_1puCo07to" rel="nofollow noreferrer">Hot end to orbit</a>. Around 2 min 30 sec the show begins.</p>

CC BY-SA 4.0
2021-07-13T18:14:01.477Z
Can you post a link to the gcode you were printing as well?
Zeiss Ikon
CC BY-SA 4.0
2021-07-13T19:31:39.597Z
G code added to git.
HerGiz
CC BY-SA 4.0
2021-07-14T11:46:47.690Z
How are you printing PLA at 175 C?  Or did I not look far enough in the gcode?
Zeiss Ikon
CC BY-SA 4.0
2021-07-14T15:18:02.937Z
At 180 C. Tried first at 200, all ok. This is a new spool. Before that one I printed with PETG at 230 C. No problems. Afcore, every print ends up the same, after 2.5 mm into print head goes inferno :)
HerGiz
CC BY-SA 4.0
2021-07-14T15:31:41.003Z
Can you try putting a shim over the Z-stop limit switch so the print starts higher, then "dry print" (no filament) to see if this still happens at the same physical height (relative to the machine frame) or after the same number of layers?
Zeiss Ikon
CC BY-SA 4.0
2021-07-14T15:38:58.320Z
Or alternately, retract or unload filament, preheat the nozzle, and jog the Z axis up 0.1 mm at a time, then wait a minute after each jog to see if the temperature starts to take off.
Zeiss Ikon
CC BY-SA 4.0
2021-07-14T16:41:58.463Z
Probably a thermistor cable fault (short-circuit). Does part of the cable flex about a particular point, or is it strapped tightly to other cables or structures? That can lead to cable failure, and thermistor cables do not seem to be particularly robust.
Mick
CC BY-SA 4.0
2021-07-14T19:22:15.863Z
@Mick That's what my suggested tests are aimed at.  Same height relative to machine frame suggests a cable fault.
Zeiss Ikon
CC BY-SA 4.0
2021-07-14T20:11:58.043Z
Ok. I see your point. Cabels are neatly packed, with that black mesh sleave. I will definitly try the test in hour or two. But... If it was cable problem, or termistor problem of any king, why do I see temperature rise at display? Last time I unplugged printer and left it on USB power, then gave it power again. During USB power temperature was going down, as soon I plugged main cable it resumed printing and temperature rising again.
HerGiz
CC BY-SA 4.0
2021-07-15T11:04:00.087Z
Thermistors read a resistance related to temperature.  If the cable shorts, that resistance goes to zero (= cold, IIRC), and if the cable disconnects, it goes to infinity (= hot).  This not just jumping suggests it isn't that simple, but my tests will still narrow down whether it's related to print time/layer steps or physical height relative to the frame.
Zeiss Ikon
CC BY-SA 4.0
2021-07-15T15:20:07.873Z
I did a test, and posted video. I edited original question.
HerGiz
<marlin><hotend><ramps-1.4><reprap>
Hotend temperature goes to infinity after few layers
HerGiz
# Hotend temperature goes to infinity after few layers

(Asked by: username_0 on 2021-07-13)

I have a "classic" home built 3D printer, Arduino Mega, RAMPS 1.4 with Marlin 2.0.

It worked, was put in storage, and now I am trying to get it running again.

During all of the testing phases, the PID autotune, etc., the temperature of the hotend is stable.

When printing, for a few layers (4-5), the temperature is OK, despite the part fan coming on and off. However, after 3-4 mm of printing the temperature just rises and rises and rises, and after 275 °C thermal protection kicks in...

MOSFETs have additional cooling and a fan over them.

I'm out of ideas... Help!!!

My config files and G-code are [here](https://github.com/hergiz/singles)

Using PrusaSlicer.

Why do I see a temperature rise on the display? Last time I unplugged the printer and left it on USB power then gave it power again. During USB power temperature was steadily going down, as soon I plugged the main cable it resumed printing and the temperature rising again.

I did another test. 20mm above bed started printing, and got same result. I captured on video entire process [Hot end to orbit](https://www.youtube.com/watch?v=5_1puCo07to). Around 2 min 30 sec the show begins.

**Tags:** marlin, hotend, ramps-1.4, reprap
> **Comments:**
> **username_1**: Can you post a link to the gcode you were printing as well?  
> **username_0**: G code added to git.  
> **username_1**: How are you printing PLA at 175 C?  Or did I not look far enough in the gcode?  
> **username_0**: At 180 C. Tried first at 200, all ok. This is a new spool. Before that one I printed with PETG at 230 C. No problems. Afcore, every print ends up the same, after 2.5 mm into print head goes inferno :)  
> **username_1**: Can you try putting a shim over the Z-stop limit switch so the print starts higher, then "dry print" (no filament) to see if this still happens at the same physical height (relative to the machine frame) or after the same number of layers?  
> **username_1**: Or alternately, retract or unload filament, preheat the nozzle, and jog the Z axis up 0.1 mm at a time, then wait a minute after each jog to see if the temperature starts to take off.  
> **username_2**: Probably a thermistor cable fault (short-circuit). Does part of the cable flex about a particular point, or is it strapped tightly to other cables or structures? That can lead to cable failure, and thermistor cables do not seem to be particularly robust.  
> **username_1**: @Mick That's what my suggested tests are aimed at.  Same height relative to machine frame suggests a cable fault.  
> **username_0**: Ok. I see your point. Cabels are neatly packed, with that black mesh sleave. I will definitly try the test in hour or two. But... If it was cable problem, or termistor problem of any king, why do I see temperature rise at display? Last time I unplugged printer and left it on USB power, then gave it power again. During USB power temperature was going down, as soon I plugged main cable it resumed printing and temperature rising again.  
> **username_1**: Thermistors read a resistance related to temperature.  If the cable shorts, that resistance goes to zero (= cold, IIRC), and if the cable disconnects, it goes to infinity (= hot).  This not just jumping suggests it isn't that simple, but my tests will still narrow down whether it's related to print time/layer steps or physical height relative to the frame.  
> **username_0**: I did a test, and posted video. I edited original question.  

---

## 2 answers

### Answer by username_0 on 2021-07-16. Score: 1 | Accepted answer

So, the problem is in fact of a hardware nature. By replacing RAMPS 1.4, the problem went away.

Arduino, firmware, G-code... everything is the same, only RAMPS was replaced.

I'm going to find a suitable MOSFET replacement.


---

### Answer by username_3 on 2021-07-14. Score: 0

Sounds like you have a short in your sensor or sensor circuitry. However, if this is the case the sensed temperature is higher than the actual hotend temperature. Does your hot end go cold when the sensed temperature takes off? A short could also show the hotend temperature going up at an unrealistically fast rate. This doesn't seem to be your case.

> **Comments:**
> **username_0**: No. When temperature goes up, so is nozzle shoveling, and after error is detected, I have to wait for the head to cool of to be able to lit Z axes it leaves a big hole around nozzle...  

---

