# Help diagnosing MODBUS TCP timeout issues

**URL:** <https://forum.inductiveautomation.com/t/help-diagnosing-modbus-tcp-timeout-issues/106792>\
**Category:** Ignition\
**Tags:** modbus, ignition81, vision\
**Created:** [May 28, 2025, 9:06pm UTC](https://forum.inductiveautomation.com/t/help-diagnosing-modbus-tcp-timeout-issues/106792 "2025-05-28T21:06:41Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![L\_F](https://avatars.discourse-cdn.com/v4/letter/l/5f8ce5/32.png) [@L\_F](https://forum.inductiveautomation.com/u/L_F)\
**Post date:** [May 28, 2025, 9:06pm UTC](https://forum.inductiveautomation.com/t/help-diagnosing-modbus-tcp-timeout-issues/106792/1 "2025-05-28T21:06:41Z")

</div>

I am trying to connect to a chiller/circulator using MODBUD over TCP. I have created the connection in the OPC UA section of my server, and I see it appear in my Vision Designer. I think I am using the write OPC path, but the tag quality is returns bad with the error:

`Bad("Bad_Timeout: The operation timed out.")`

I want to make sure that I've configured the tag correctly. Please see below:

 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/f/5/f50e1ec25b7ffa75d5d7a3cbdb22f26a0241c145.png)

 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/d/a/daa1f5e1bcca649df8a59b08d571b202d34af04e.png)

 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/f/a/faadbd1a2d84aa747c3f7c5697fbd38bbe4db5bf.png)

My server logs are full of timeouts and even some disconnections:

 ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/c/c/cccfb1f5077a2d80e8ed5c503d2ff17b9c6774dc.png)

Not really sure where to start in debugging this. These same messages are seen in my log files.

---

<div class="post-metadata">

**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\
**Post date:** [May 28, 2025, 9:08pm UTC](https://forum.inductiveautomation.com/t/help-diagnosing-modbus-tcp-timeout-issues/106792/2 "2025-05-28T21:08:36Z")

</div>

Have you tried a different unit id (address `1.IRUI1` for example)?

Do you have any other Modbus software that can successfully communicate (Modpoll, or similar)?

---

<div class="post-metadata">

**Author:** ![L\_F](https://avatars.discourse-cdn.com/v4/letter/l/5f8ce5/32.png) [@L\_F](https://forum.inductiveautomation.com/u/L_F)\
**Post date:** [May 28, 2025, 9:14pm UTC](https://forum.inductiveautomation.com/t/help-diagnosing-modbus-tcp-timeout-issues/106792/3 "2025-05-28T21:14:40Z")

</div>

I needed to add the unit ID to the tag path. Thanks!