MODBUS sensors unavailable occasionally then they come back after a recent OS update

Configuration
1

Hey all,

I’ve had a MODBUS integration with SMA working flawlessly for a few years. But at some point I did an OS update and since then I’ve had all modbus sensors fail to load and show “Unavailable” randomly a few times a day. All readings work fine, then at some point all of them fail for a while (a few minutes or up to an hour sometimes), then they come back.

I’m reading about 15 registers.

There were no errors prior to updating to the latest HA OS about 6 months ago. OR at least if there were, it never resulted in prolonged outage. All data was always up to date.

Any ideas?

----------------------------- ERROR 1 -----------------------------

Logger: pymodbus.logging
Source: runner.py:156
First occurred: 23 July 2026 at 06:57:14 (125 occurrences)
Last logged: 15:58:11

Failed to connect
Repeating…

----------------------------- ERROR 2 -----------------------------

Logger: homeassistant.components.modbus
Source: components/modbus/modbus.py:310
integration: Modbus (documentation, issues)
First occurred: 22 July 2026 at 13:25:45 (104739 occurrences)
Last logged: 16:03:11

  • Pymodbus: SI6: Error: device: 3 address: 30843 → Modbus Error: [Connection] Not connected[AsyncModbusTcpClient 192.168.1.22:502]
  • Pymodbus: SI6: Error: device: 3 address: 30851 → Modbus Error: [Connection] Not connected[AsyncModbusTcpClient 192.168.1.22:502]
  • Pymodbus: SI6: Error: device: 3 address: 30783 → Modbus Error: [Connection] Not connected[AsyncModbusTcpClient 192.168.1.22:502]
  • Pymodbus: SI6: Error: device: 3 address: 30803 → Modbus Error: [Connection] Not connected[AsyncModbusTcpClient 192.168.1.22:502]
  • Pymodbus: SI6: Error: device: 3 address: 30859 → Modbus Error: [Connection] Not connected[AsyncModbusTcpClient 192.168.1.22:502]

----------------------------- ERROR 3 -----------------------------

Logger: pymodbus.logging
Source: components/modbus/modbus.py:391
First occurred: 22 July 2026 at 13:25:45 (96 occurrences)
Last logged: 14:33:38

  • No response received after 3 retries, continue with next request >>>>> send: 0xc3 0xe3 0x0 0x0 0x0 0x6 0x3 0x3 0x78 0x37 0x0 0x2 >>>>> recv: 0xc3 0xe3 0x0 0x0 0x0 0x7 0x3 0x3 0x4 0x0 0x0 0x9 0x7f extra data: >>>>> send: 0xc3 0xe4 0x0 0x0 0x0 0x6 0x3 0x3 0x78 0x37 0x0 0x2 >>>>> recv: 0xc3 0xe4 0x0

----------------------------- ERROR 4 -----------------------------

Logger: homeassistant.util.logging
Source: util/logging.py:74
First occurred: 23 July 2026 at 06:57:13 (1 occurrence)
Last logged: 23 July 2026 at 06:57:13

Module homeassistant.components.modbus is logging too frequently. 200 messages since last count

----------------------------- ERROR 5 -----------------------------

Logger: homeassistant.components.template.template_entity
Source: components/template/template_entity.py:101
integration: Template (documentation, issues)
First occurred: 19:39:37 (2 occurrences)
Last logged: 19:39:37

  • TemplateError(‘ValueError: Template error: float got invalid input ‘unavailable’ when rendering template ‘{{ (states(‘sensor.sma_30903_voltage_external_power_connection_phase_a’) | float * states(‘sensor.sma_30985_total_current_external_network_connection’) | float / 1000) | round(3) }}’ but no default was specified’) while processing template ‘Template<template=({{ (states(‘sensor.sma_30903_voltage_external_power_connection_phase_a’) | float * states(‘sensor.sma_30985_total_current_external_network_connection’) | float / 1000) | round(3) }}) renders=18>’ for attribute ‘_attr_native_value’ in entity ‘sensor.generator_power’
  • TemplateError(‘ValueError: Template error: float got invalid input ‘unavailable’ when rendering template ‘{{ ((states(‘sensor.generator_power’) | float + states(‘sensor.solar_power’) | float) - states(‘sensor.battery_load’) | float) | round(3) }}’ but no default was specified’) while processing template ‘Template<template=({{ ((states(‘sensor.generator_power’) | float + states(‘sensor.solar_power’) | float) - states(‘sensor.battery_load’) | float) | round(3) }}) renders=66>’ for attribute ‘_attr_native_value’ in entity ‘sensor.house_load’

----------------------------- ERROR 4 -----------------------------

Logger: homeassistant.components.modbus
Source: components/modbus/modbus.py:310
integration: Modbus (documentation, issues)
First occurred: 19:39:37 (1 occurrence)
Last logged: 19:39:37

Pymodbus: SI6: Error: device: 3 address: 30903 → Modbus Error: [Input/Output] No response received after 3 retries, continue with next request

2

On the surface it looks like a network or device issue, are there any accessible logs on the device? Can you power cycle the device / network gear?

It’s also possible it’s a modbus protocol thing that’s changed. We’d want a log with debug enabled that show this occurring.

3

It kind of looks like it, but the outages only started immediately as of the HA Core update. Also I note, these errors are happening throughout the day, but at some point the whole thing just shuts down and comes back after a while. Meantime I can still it MIDBUS with the modbus poll app. I’m wondering if the errors were always there, but HA is dropping out occasionally and is totally unrelated to those errors.

4

There was a major rework of modbus recently. Post your debug log here first or create an issue.

5

Thanks. I kind of thought I provided a lot of info above. Where else can I get debug logs from?