406 on a Fronius International GmbH Fronius SnapINverter: Power stage set temperature sensor faulty
Short answer
On a Fronius International GmbH inverter, 406 means: Power stage set temperature sensor faulty. The inverter stops until the fault clears or is reset. An engineer is needed to fix the cause.
Reviewed 24 September 2026 · 1 source
What it means
The manual says: Power stage set temperature sensor faulty.
Part involved: inverter electronics.
When it shows: Class 4 status code.
Likely causes:
- The inverter will automatically attempt to connect again and, if possible, resume feeding in; if displayed all the time notify a Fronius-trained service engineer.
Is it safe?
| Does the inverter stop? | Yes |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
| Engineer needed? | Yes |
The inverter stops until the fault clears or is reset.
Resetting itself: yes.
Manual reset: Automatic when condition clears.
What you can check
- Read the state code on the inverter display or in Fronius Solar.web and note date/time for your installer.
- If the code shows all the time, contact your installer.
What the engineer will check
- Fronius Service diagnosis (power stage, sensors, control boards); check grid for 453/454.
Who to ask for: Fronius-trained PV installer / Fronius Service Partner.
Certification: Qualified electrician (BS 7671; MCS-certified PV installer for work on the PV array/DC side).
What you might notice
Sources
- Fronius Primo 3.0-1 - 8.2-1 Operating Instructions (HTML) ↗ · 42,0410,2165 online edition · Reviewed 24 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 24 September 2026