Usually self-clears

Sunsynk F35: No AC Grid / No Utility

Updated June 2026 · Reviewed for technical accuracy · ~3 min read

F35 is the Sunsynk telling you it can't see the utility grid. On a grid-tied setup it then stops exporting and waits. Most of the time this is not a fault at all: it is a power cut or a breaker that tripped between the inverter and the grid. When mains power comes back, F35 normally clears by itself.

Grid, wiring, or inverter?

F35 sits firmly on the grid side. Most likely first:

A utility outage. Check whether the rest of the house is also dark. If the whole place is out, it is load-shedding or a cut, just wait.
A tripped breaker or open isolator on the line between the inverter and the meter.
A loose AC connection at the inverter or distribution board.
Grid voltage or frequency out of limits, where the supply is too unstable for the inverter to connect.

How to check it safely

Outside only These steps use the breakers and your eyes. Don't open the inverter or touch wiring.

Is the power out? Look at the rest of the house or ask a neighbour. If the grid is down, F35 will clear when power returns. Nothing to fix.
Check the AC breaker and isolator between the inverter and the grid. Make sure it is on, and reset it if it tripped.
Confirm the main supply by checking the main breaker and meter have power.
Allow the reconnection delay. After power returns, the Sunsynk waits a short, standards-required time before it comes back online. This pause is normal.
Grid present but F35 stays? Do a safe power cycle (AC off, DC isolator off, wait five minutes, restart). If it still won't connect, the AC connection or grid-detection may need a look.

Quick decision flowchart

F35 appears

↓ is the rest of the house also without power?

✅ Yes, whole house out → it's a grid cut or load-shedding. Wait; F35 clears when power returns.

❌ No, house has power → check the AC breaker/isolator to the inverter.

↓ breaker on, grid present, still F35

Power-cycle once. If it still won't connect, your installer should check the AC connection and grid settings.

When to bring in a professional If the grid is clearly there (house has power, breaker on) and F35 keeps returning after a restart, the AC wiring connection or the inverter's grid-detection circuit may need service. That's an installer job.

Related Sunsynk codes

F42, AC line low voltage F47, AC over frequency F18, AC overcurrent

FAQ

F35 shows but my house has power.

The inverter sees the grid only through its own AC connection. If a breaker or isolator on that line is off, or a connection is loose, it reads "no grid" even though the house is powered. Check that breaker first.

Will my system run on battery during F35?

On a hybrid Sunsynk with backup, the battery keeps your backup loads going during a real outage. F35 simply reflects that the grid is absent; the inverter reconnects when mains returns.

How long until F35 clears after power is back?

Grid-tied inverters wait a short, standards-required reconnection delay (often a few minutes) once the grid is stable. A brief wait is normal.

Sources

Sunsynk Hybrid Inverter User Manual (F35 = No AC grid / no utility; confirm grid status and AC connections).
Sunsynk fault-code references and installer documentation.

⚠️ Safety disclaimer. Solar inverters carry lethal DC and AC voltage even when "off". This guide covers external, switch-level steps only. Never open the unit or work on wiring unless qualified. When in doubt, call a licensed installer or electrician.