<p>I have an Ender 3 Pro with a Bigtree SKR board. I just replaced the entire hot end (thermistor, heating element, Micro Swiss hotend).</p>
<p>Now when I try to print a Benchy everything seems fine until maybe the 3rd or 4th layer. Then the PLA stops flowing so I stop the print and the temperature flies back up from 220 to 260 °C on its own (I do not want to print at 260 °C, I want to print at 220 °C). This makes me assume the PLA is stopping because the temperature is too hot.</p>
<p>What would cause this? Did I wreck the thermistor when I was putting it in? Is it a firmware issue? Why isn't runaway protection turning it off?</p>

CC BY-SA 4.0
2020-10-13T02:04:54.133Z
You print PLA at 260°C? What did you modify? Did you install the proper firmware in swapping the hotend? Installing firmware is not optional.
Trish
CC BY-SA 4.0
2020-10-13T02:10:22.380Z
210-230 is most likely ABS and not PLA. PLA is 190-210.
Trish
CC BY-SA 4.0
2020-10-13T02:31:00.557Z
The specs on the site you link read Print Temperature
190C - 220C
Plate Temperature
60 - 80C
Extruder Temperature
200C - 220C and are rather typical for PLA. the sticker 210-320 you quote however sounds ABS-y
Trish
CC BY-SA 4.0
2020-10-13T02:41:10.490Z
Let us [continue this discussion in chat](https://chat.stackexchange.com/rooms/115043/discussion-between-jackie-and-trish).
Jackie
CC BY-SA 4.0
2020-10-13T02:45:58.000Z
@Tish reading back I see the problem, I am not printing at 260. The OS states it is at 220 but when I cancel it flies back up. I don't want it to print at 260 just to be clear.
Jackie
CC BY-SA 4.0
2020-10-13T09:17:26.877Z
@Jackie And your target temp is 220° all along? Sounds like a wonky thermistor, or perhaps excessive part cooling / unisolated heater block / terrible PID tune.
towe
CC BY-SA 4.0
2020-10-13T18:02:58.427Z
@towe my guess is the thermistor is the issue going to try and replace out later. Can you talk more about the unisolated heater block? Does that mean I didn't properly set the block with the grub screw? Also what is PID tuning?
Jackie
CC BY-SA 4.0
2020-10-14T04:59:06.513Z
@Jackie Depending on your part cooling fan, the air flow of that might directly hit your heater block and nozzle - cooling it down excessively, which could cause the lack of extrusion. The board tries to compensate for that by heating far more than would normally be required. When you then stop the print, the heat shoots up due to the previous heating.
The fix would be a better part cooling duct, or one of the silicone socks you can put over your heater block to better insulate it.
PID refers to how the controller board calculates how much to heat the nozzle to maintain a stable temperature.
towe
CC BY-SA 4.0
2020-10-14T04:59:33.273Z
You can tune those values if your temperature fluctuates greatly, but I don't think this is your (main) issue.
towe
CC BY-SA 4.0
2020-10-14T13:13:27.120Z
@towe interesting, could that be an issue if the silicon sock was slightly off? I did notice it was a little offset.
Jackie
<troubleshooting><hotend><thermistor><all-metal-hotend>
Why does Marlin report the wrong temperature until print is stopped?
Jackie
# Why does Marlin report the wrong temperature until print is stopped?

(Asked by: username_0 on 2020-10-13)

I have an Ender 3 Pro with a Bigtree SKR board. I just replaced the entire hot end (thermistor, heating element, Micro Swiss hotend).

Now when I try to print a Benchy everything seems fine until maybe the 3rd or 4th layer. Then the PLA stops flowing so I stop the print and the temperature flies back up from 220 to 260 °C on its own (I do not want to print at 260 °C, I want to print at 220 °C). This makes me assume the PLA is stopping because the temperature is too hot.

What would cause this? Did I wreck the thermistor when I was putting it in? Is it a firmware issue? Why isn't runaway protection turning it off?

**Tags:** troubleshooting, hotend, thermistor, all-metal-hotend

> **Comments:**
> **username_1**: You print PLA at 260°C? What did you modify? Did you install the proper firmware in swapping the hotend? Installing firmware is not optional.  
> **username_1**: 210-230 is most likely ABS and not PLA. PLA is 190-210.  
> **username_1**: The specs on the site you link read Print Temperature 190C - 220C Plate Temperature 60 - 80C Extruder Temperature 200C - 220C and are rather typical for PLA. the sticker 210-320 you quote however sounds ABS-y  
> **username_0**: Let us [continue this discussion in chat](https://chat.stackexchange.com/rooms/115043/discussion-between-username_0-and-username_1).  
> **username_0**: @Tish reading back I see the problem, I am not printing at 260. The OS states it is at 220 but when I cancel it flies back up. I don't want it to print at 260 just to be clear.  
> **username_2**: @username_0 And your target temp is 220° all along? Sounds like a wonky thermistor, or perhaps excessive part cooling / unisolated heater block / terrible PID tune.  
> **username_0**: @username_2 my guess is the thermistor is the issue going to try and replace out later. Can you talk more about the unisolated heater block? Does that mean I didn't properly set the block with the grub screw? Also what is PID tuning?  
> **username_2**: @username_0 Depending on your part cooling fan, the air flow of that might directly hit your heater block and nozzle - cooling it down excessively, which could cause the lack of extrusion. The board tries to compensate for that by heating far more than would normally be required. When you then stop the print, the heat shoots up due to the previous heating. The fix would be a better part cooling duct, or one of the silicone socks you can put over your heater block to better insulate it. PID refers to how the controller board calculates how much to heat the nozzle to maintain a stable temperature.  
> **username_2**: You can tune those values if your temperature fluctuates greatly, but I don't think this is your (main) issue.  
> **username_0**: @username_2 interesting, could that be an issue if the silicon sock was slightly off? I did notice it was a little offset.  

---

## 0 answers

