# Laser module won't light

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**📅Update: 2020/09/28**
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### Potential reasons:

1. The P5 cable is loose. 
2. The laser module is defective. 
3. The front end board is defective.
4. The DexArm motherboard is defective.

### Diagnose steps:

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**Notice:** wear the Safety Goggles before setting up and throughout the laser engraving process!
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1. Connect your DexArm to Rotrics Studio.
2. Plugin the laser module.
3. Check if the laser fan is running or not. 
4. Open **Terminal** and send **`M3 S255`** and check if the laser is on. 
5. If not, switch to 3D printing module, send **`M3 S255`** via Terminal, and see if the fan in front of 3D module is running or not. 

<div align="left"><img src="https://2132465959-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LtPFIBncU5l4J8tl5Yh%2F-MIHb06QlKgXQsJ4t3Yi%2F-MIHeLoJdBFdg0kef5Br%2Fimage.png?alt=media&#x26;token=77ef89c7-a0e3-4731-a965-d6e887b9c8fa" alt=""></div>

### Analysis

1\. If the laser fan is not running after power on, please unscrew the Arm base plate and check if the following P5 cable is connected or not. If it is loose, pls connect it, and then retry the laser module.  If it is connected, then the motherboard and front end board need to be replaced. Please email <support@rotrics.com> about the problem.&#x20;

![](https://2132465959-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-LtPFIBncU5l4J8tl5Yh%2F-MLv3MKoCQG6iJepaLH_%2F-MLvCMaZqJ3u8fggv3W1%2F%E5%BE%AE%E4%BF%A1%E5%9B%BE%E7%89%87_20201112144618.png?alt=media\&token=c2b56910-5835-439a-ad46-89a2cb7bab36)

2\. If the laser fan is working after power on and the laser module starts to emit light after sending the command **`M3 S255`**,  then pls re-try laser engraving by following our user manual.

3\. If the laser fan is working after power on, but the laser module still won't light with command **`M3 S255`**, and after switching to 3D printing module, the fan in front of 3D module works under this command, then the laser module is defective. please email <support@rotrics.com> with the relevant image/videos and we will help you to make it right.&#x20;

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