<p>I dont want the part cooling fan on during preheat, especially when I'm only heating the bed, it is just unnecessarily loud and serves no purpose at that time.</p>

<p>However when I set <code>PREHEAT_1_FAN_SPEED</code> to 0 it has no effect, the fan still spins at full speed as soon as I preheat either the hotend or the bed.</p>

<p>So why is this setting not working and how do I fix this?</p>

<p>I am using the latest version of <a href="https://github.com/MarlinFirmware/Marlin/tree/1.1.x/Marlin" rel="nofollow noreferrer">Marlin</a>.</p>

<p>The only one that is defined is the one that I am editing and it is the one that appears on line ~1260 of the stock configuration.h</p>

<pre><code>#define PREHEAT_1_FAN_SPEED 0 // Value from 0 to 255
</code></pre>

<p>And this is the grep result of searching the entire firmware folder:</p>

<p><a href="https://i.stack.imgur.com/dJh5p.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/dJh5p.png" alt="grep results"></a></p>

This answer is now obsolete now that the OP has updated the question with additional information. It is left here as a possible solution for those who have tinkered with there firmware.
Part cooling fan speed during preheat (from menu) is controlled by the setting
```
```
#define PREHEAT_1_FAN_SPEED     0 // Value from 0 to 255
```
```
in
Configuration.h
where a value of
```
0
```
implies no rotation, or 0 % and
```
255
```
implies 100 %.
If changing this value in your configuration does not result in a reduced fan speed, you could have this constant be defined somewhere else overriding this value.