SG04LP3/SG05LP1 hybrid families and SG01HP3-EU-DM2
Deye F42 error code
On SG04LP3/SG05LP1, the grid/AC line voltage is below the configured low-voltage limit; on SG01HP3-DM2 firmware F42 instead reports a parallel software-version mismatch.
Likely causes
- Weak grid or sustained low grid voltage
- Undersized AC cable causing voltage drop
- Loose AC terminals
- Mismatched firmware between paralleled SG01HP3 units
Checks to run, in order
- 1Measure the grid voltage at the inverter AC input
- 2Check the AC cable size and terminal torque
- 3Check the grid standard and voltage window setting
- 4If paralleled on SG01HP3, compare firmware versions
Fixes
- Correct the low grid voltage within the allowed window
- Tighten or replace the AC cable
- Update all parallel units to the same firmware
When to escalate
If voltage and firmware match specification and F42 persists, the distributor should review the grid settings.
Fix it with the right tools
Check the system around the fault before replacing parts: load, battery bank, PV string and commissioning settings. If you need a second opinion, send the code and your inverter model to our team.
Before you open the inverter
- Isolate both the AC and DC sides, then confirm the display is dead before touching terminals.
- Use insulated tools and one hand where possible. DC arcs do not self-extinguish like AC.
- If you see burnt terminals, swollen cells, leaking electrolyte or a burning smell, stop and escalate instead of resetting the fault.
Questions installers ask
What does Deye F42 mean?
On SG04LP3/SG05LP1, the grid/AC line voltage is below the configured low-voltage limit; on SG01HP3-DM2 firmware F42 instead reports a parallel software-version mismatch.
How do I fix Deye F42?
Correct the low grid voltage within the allowed window Tighten or replace the AC cable Update all parallel units to the same firmware
When should I escalate Deye F42?
If voltage and firmware match specification and F42 persists, the distributor should review the grid settings.
Can I reset Deye F42 myself?
Only after isolating the AC and DC sides and running the checks above. If Deye F42 returns immediately, stop resetting it and escalate; a repeating fault usually points to a real circuit, battery or hardware problem.
Which models show Deye F42?
Deye F42 is documented for SG04LP3/SG05LP1 hybrid families and SG01HP3-EU-DM2. Confirm the code on your own unit's display or manual before ordering parts.
More Deye error codes
- Deye F01PV input polarity is reversed at one or both DC inputs.
- Deye F02PV insulation resistance to earth is below the safety limit.
- Deye F03Ground fault detected on the PV array (GFDI).
- Deye F04GFDI ground-failure alarm: the PV array or inverter is not properly earthed.
- Deye F05Control-board EEPROM read failure.
- Deye F06Control-board EEPROM write failure.
Guidance reviewed 17 October 2026 by the Mishka Energy installer team. Error codes vary by brand, model family and firmware; confirm against the manufacturer manual.
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