<p>I had a similar problem and there could be three reasons(if the connections are ok):</p>

<ul>
<li>thin wires to the hotend</li>
<li>one of the MOSFETs was fried </li>
<li>the termal sensor wasn't good enough insert into the hotend</li>
</ul>

<p>Try to measure the hotend heating element voltage while printing.</p>

CC BY-SA 3.0
2018-02-24T16:34:55.820Z
One of the mosfets on the board was bad. Just replaced the board and the problem was solved.
B.Schoch
CC BY-SA 3.0
2018-02-14T06:29:01.257Z
2018-02-14T07:48:18.033Z
2018-02-14T07:48:18.033Z
Coder_fox
<p>This really looks like a bad connection, so try with your old board to see if the broken connection is on the board, or it's the temp sensor or the wires.</p>

<p>I had exactly this problem with a bad connection from the temp sensor.</p>

<p>If you didn't break anything, it's the board that's fried / badly connected.</p>

CC BY-SA 3.0
2018-02-15T08:58:25.433Z
2018-02-15T08:58:25.433Z
Valmond
<p>I recently rebuilt my A8 printer to have a metal frame and replaced the board with a GT2560 reva+. I'm having problems with the temp readings from both my hotend and hotbed. Using marlin 1.1x and Its possible I have something configured incorrectly. I can get successful prints with good quality but sometimes I get thermal runaway during a print.</p>

<p>Both cold and at temp (200c) have fairly large temp spikes. I didn't have this problem with my old board. I had much smoother temp curves. I'm using the default PID values for Ultimaker Kp 22.2, Ki 1.08, Kd 144.</p>

<p>I have tried to use PID autotune but get drastically different values every time I run it and using the results gave worse results (sometimes giving a heating error during the autotune). I checked all the wiring and nothing looks frayed or damaged. </p>

<p>First pic is cold temps. Second is trying to do a PID tune. Third and fourth are during a print.</p>

<p><a href="https://i.sstatic.net/7H8KC.png" rel="noreferrer"><img src="https://i.sstatic.net/7H8KC.png" alt="Temps cold"></a></p>

<p><a href="https://i.sstatic.net/EpW8E.png" rel="noreferrer"><img src="https://i.sstatic.net/EpW8E.png" alt="PID tune"></a></p>

<p><a href="https://i.sstatic.net/A9bU0.png" rel="noreferrer"><img src="https://i.sstatic.net/A9bU0.png" alt="During a print"></a></p>

<p><a href="https://i.sstatic.net/GwyP4.png" rel="noreferrer"><img src="https://i.sstatic.net/GwyP4.png" alt="During a print 2"></a></p>

CC BY-SA 3.0
2018-02-14T09:08:18.327Z
Are you sure the fourth is during a print? Looks like PID auto tune to me.
Valmond
<hotend>
Spiky hotend and bed temps
B.Schoch
# Spiky hotend and bed temps

(Asked by: username_0 on 2018-02-13)

I recently rebuilt my A8 printer to have a metal frame and replaced the board with a GT2560 reva+. I'm having problems with the temp readings from both my hotend and hotbed. Using marlin 1.1x and Its possible I have something configured incorrectly. I can get successful prints with good quality but sometimes I get thermal runaway during a print.

Both cold and at temp (200c) have fairly large temp spikes. I didn't have this problem with my old board. I had much smoother temp curves. I'm using the default PID values for Ultimaker Kp 22.2, Ki 1.08, Kd 144.

I have tried to use PID autotune but get drastically different values every time I run it and using the results gave worse results (sometimes giving a heating error during the autotune). I checked all the wiring and nothing looks frayed or damaged.

First pic is cold temps. Second is trying to do a PID tune. Third and fourth are during a print.

[![Temps cold](https://i.sstatic.net/7H8KC.png)](https://i.sstatic.net/7H8KC.png)

[![PID tune](https://i.sstatic.net/EpW8E.png)](https://i.sstatic.net/EpW8E.png)

[![During a print](https://i.sstatic.net/A9bU0.png)](https://i.sstatic.net/A9bU0.png)

[![During a print 2](https://i.sstatic.net/GwyP4.png)](https://i.sstatic.net/GwyP4.png)

**Tags:** hotend

> **Comments:**
> **username_1**: Are you sure the fourth is during a print? Looks like PID auto tune to me.  

---

## 2 answers

### Answer by username_2 on 2018-02-14. Score: 2 | Accepted answer

I had a similar problem and there could be three reasons(if the connections are ok):

* thin wires to the hotend
* one of the MOSFETs was fried
* the termal sensor wasn't good enough insert into the hotend

Try to measure the hotend heating element voltage while printing.

> **Comments:**
> **username_0**: One of the mosfets on the board was bad. Just replaced the board and the problem was solved.  

---

### Answer by username_1 on 2018-02-15. Score: 1

This really looks like a bad connection, so try with your old board to see if the broken connection is on the board, or it's the temp sensor or the wires.

I had exactly this problem with a bad connection from the temp sensor.

If you didn't break anything, it's the board that's fried / badly connected.


---

