# OPC tags don't always change value of the related OPC item

**URL:** <https://forum.inductiveautomation.com/t/opc-tags-dont-always-change-value-of-the-related-opc-item/75417>\
**Category:** Ignition\
**Created:** [June 22, 2023, 6:51pm UTC](https://forum.inductiveautomation.com/t/opc-tags-dont-always-change-value-of-the-related-opc-item/75417 "2023-06-22T18:51:15Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Emile\_Laplante](https://avatars.discourse-cdn.com/v4/letter/e/c57346/32.png) [@Emile\_Laplante](https://forum.inductiveautomation.com/u/Emile_Laplante)\
**Post date:** [June 22, 2023, 6:51pm UTC](https://forum.inductiveautomation.com/t/opc-tags-dont-always-change-value-of-the-related-opc-item/75417/1 "2023-06-22T18:51:16Z")

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Hi,

I created an OPC tag that is link to an item from my plc which was created with an OPC server. I pass this OPC tag to a pop up window. When I click on a button in the pop up window, I set the OPC tag to True with this line of code in the script :

```auto
event.source.parent.fvnr.commands.man_start_stop = True

```

The value in the PLC changes most of the time, but sometime, it dosen't. I need to close the pop up window, then re-open it. What is the issue? Is there a better way to change the value of the item?

Thank you!

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<div class="post-metadata">

**Author:** ![justinedwards.jle](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/justinedwards.jle/32/37854_2.png) [@justinedwards.jle](https://forum.inductiveautomation.com/u/justinedwards.jle)\
**Post date:** [June 22, 2023, 7:28pm UTC](https://forum.inductiveautomation.com/t/opc-tags-dont-always-change-value-of-the-related-opc-item/75417/2 "2023-06-22T19:28:00Z")

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What is `man_start_stop`? Is this a custom property with a bidirectional binding to your OPC tag? Perhaps it would be better to use `system.tag.writeBlocking`, and write the value directly to the tag instead of relying on the binding.