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Deye F18: AC Overcurrent Fault (Hardware)

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

Your Deye inverter shut down and shows F18 because it sensed more current on its AC output than the hardware is allowed to pass, so it cut off to protect itself. In most cases it's caused by too much load (or a sudden surge) on the backup/EPS output, not a broken inverter. It's usually fixable in a few minutes.

Is it you, the grid, or the inverter?

F18 is almost always on the load side. The usual triggers, most common first:

  • A surge when a big appliance starts. A pump, motor, compressor, A/C or microwave kicking on draws a big inrush current.
  • Too much connected to the backup (EPS) output. The total load is above the inverter's rating.
  • A faulty appliance shorting or drawing abnormal current.
  • Rarely, an internal hardware fault. Only suspect this if F18 keeps coming back with little or no load.

The safe fix, step by step

Before you start Don't open the inverter and don't touch DC wiring. Everything below is done from the outside, with the switches.
  1. Reduce the load. Switch off heavy appliances on the backup/EPS circuit, anything with a motor or heating element first.
  2. Power-cycle the AC side. Turn the inverter's AC output breaker off, wait 60 seconds, then turn it back on.
  3. If F18 is still there, do a full restart. Turn off the AC breaker, then the DC isolator (the switch from the panels and battery), wait 5 minutes, then turn the DC isolator back on, then the AC breaker.
  4. Bring loads back one at a time. Re-enable appliances one by one and watch which one trips it. That's your culprit.
  5. Confirm you're within the rating. Check that the total backup load is below your inverter's rated output power (on the spec label or manual).

Quick decision flowchart

F18 appears
↓ reduce load & power-cycle (steps 1 to 3)
✅ Cleared and stays off with sensible load → you're good. Keep backup load within rating.
❌ Returns, even with light or no load → likely an internal hardware fault.
↓
If it keeps returning, stop resetting it and call your installer.
When to stop and call a professional If F18 comes back immediately with almost nothing connected, or it returns again and again after a proper restart, the inverter's output stage may be damaged. Don't keep power-cycling a hardware fault. Contact your installer or Deye support with the code and your model number.

Related Deye codes

F34, AC overcurrent F20, DC overcurrent F64, Heatsink high temp

FAQ

F18 won't clear even after a full restart. Now what?

Disconnect all backup loads and restart once more. If F18 still appears with nothing connected, it's no longer a load problem, it points to the inverter's internal AC output stage. Stop resetting and contact your installer.

Can I just ignore F18 and keep using grid power?

The inverter protects itself by shutting the affected output, so you may lose backup/EPS power until it's resolved. Ignoring repeated F18 events risks further damage, so diagnose the load or get it checked.

Did F18 damage my appliances?

Usually no. The fault is the inverter protecting itself by cutting off quickly. But if a specific appliance triggers F18 every time, have that appliance inspected.

Sources

  • Deye Hybrid Inverter User Manual (fault-code table, F18 = "AC over current fault of hardware").
  • Deye dealer technical references for F-series fault codes.
⚠️ 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 you're qualified. When in doubt, call a licensed solar installer or electrician.