# Cannot write values to Prosys OPC UA server variables

**URL:** <https://discourse.nodered.org/t/cannot-write-values-to-prosys-opc-ua-server-variables/58026>\
**Category:** General\
**Created:** [9 February 2022 11:51 UTC](https://discourse.nodered.org/t/cannot-write-values-to-prosys-opc-ua-server-variables/58026 "2022-02-09T11:51:18Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Tevel](https://avatars.discourse-cdn.com/v4/letter/t/ee59a6/32.png) [@Tevel](https://discourse.nodered.org/u/Tevel)\
**Post date:** [9 February 2022 11:51 UTC](https://discourse.nodered.org/t/cannot-write-values-to-prosys-opc-ua-server-variables/58026/1 "2022-02-09T11:51:18Z")

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Hello everyone.

I am new at Node-Red and I have trouble writing values to variables on the Prosys OPC UA server.  
Reading values is working alright.

I have the following structure. Inject seems to work yet the value on the OPC server does not change.  
No errors are recorded

![image](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/7/d/7d3699a176d160b208e684fdd0546dcbb9634fc5.png)

Here is the picture of the settings. Variable in OPC is set to "constant".

 ![image](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/3X/4/c/4ca060b4f29793cd4d6597fffe74d4b428ccead6.png)

Any idea on why I cannot write to OPC will be greatly appreciated.  
Also if you need any further information from my side, please let me know.

Thank you

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<div class="post-metadata">

**Author:** ![Tevel](https://avatars.discourse-cdn.com/v4/letter/t/ee59a6/32.png) [@Tevel](https://discourse.nodered.org/u/Tevel)\
**Post date:** [10 February 2022 10:31 UTC](https://discourse.nodered.org/t/cannot-write-values-to-prosys-opc-ua-server-variables/58026/2 "2022-02-10T10:31:06Z")

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I have found the solution.

Before, OPC UA client, you need to add OPC UA Item block where you define a tag to write to.

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<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/flex026/uploads/nodered/original/1X/d073cd938eafa2e558d7c2cd59003b3ef4963033.png) [@system](https://discourse.nodered.org/u/system)\
**Post date:** [11 April 2022 10:31 UTC](https://discourse.nodered.org/t/cannot-write-values-to-prosys-opc-ua-server-variables/58026/3 "2022-04-11T10:31:42Z")

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