F64 on a Sunsynk ECCO single-phase hybrid SG05LP1: Heat sink temperature too high
Short answer
On a Sunsynk inverter, F64 means: Heat sink temperature too high. The inverter stops until the fault clears or is reset.
Reviewed 24 September 2026 · 1 source
What it means
The manual says: Heat sink temperature too high.
Part involved: heat sink / cooling.
When it shows: Heat sink over-temperature.
Likely causes:
- Overloading; poor ventilation; blocked fan; hot surroundings.
Is it safe?
| Does the inverter stop? | Yes |
|---|---|
| Severity | Fault — clears by itself when the condition goes |
The inverter stops until the fault clears or is reset.
Resetting itself: yes.
Manual reset: Turn off the inverter for 30 minutes and restart.
What you can check
- Read the full code and message on the inverter screen or in the Sunsynk Connect app and note the date/time for your installer.
- Check the inverter's AC isolator next to the inverter and the solar/battery breaker in the consumer unit are ON (do not reset a breaker that trips again - call your installer).
- Check the inverter is not covered or boxed in and the space is not unusually hot (look only).
What the engineer will check
- Check ventilation, fan, load profile.
Who to ask for: Qualified electrician / MCS PV installer.
Certification: Battery and hybrid-inverter DC work: installer trained/approved by the manufacturer; electrical work under BS 7671 by a competent person.
What you might notice
Sources
- Fault Codes Causes & Solutions Version 1.0 ↗ · Version 1.0 · page 12 · Reviewed 24 September 2026
A code explains what the controller detected, not a confirmed root cause.
Reviewed: 24 September 2026