42Fault

DEYE inverter error 42 (F042)

AC Line W,U low voltage

Also displayed as F042 / F42 on some models.

Faultthe inverter cuts its output and the red LED stays solid until the fault is cleared.

The exact meaning depends on your model:

Also applies to:SUN-120K-G01P3-EU-BM8SUN-125K-G01P3-EU-BM8SUN-130K-G01P3-EU-BM8SUN-135K-G01P3-EU-BM8SUN-136K-G01P3-EU-BM8SUN-7K-G02P1-EU-AM2SUN-7.5K-G02P1-EU-AM2SUN-8K-G02P1-EU-AM2+18

What it means

AC Line W,U low voltageThe W-U line voltage is below the protection setting.

Cause: The line voltage between phases W and U is below the protection setting; loose or incorrectly connected AC cables can cause the low reading.

How to fix it

  1. Check the AC voltage protection setting.
  2. Check the voltage difference between the LCD and a meter, and check whether all AC cables are firmly and correctly connected.

Source: 041_BManual_SUN-120_125_130_135_136K-G01P3-EU-BM8_20251021_en_a2166559.pdf, p.63 · 065_BManual_SUN-7_7.5_8K-G02P1-EU-AM2_20260625_en_4466f08b.pdf, p.52 · 032_BManual_SUN-9_10_10.5K-G02P1-EU-AM2_20260625_en_df0f2106.pdf, p.52 · +4 more official manuals

Also applies to:SUN-6K-G06-LV-P1SUN-8K-G06-LV-P1SUN-6K-G06P3-EU-BM2-LV-P1SUN-8K-G06P3-EU-BM2-LV-P1SUN-10K-G05-LVSUN-12K-G05-LVSUN-15K-G05-LVSUN-15K-G06P3-EU-BM2-P1+71

What it means

AC Line W,U low voltageThe line voltage between phases W and U is below the protection setting.

Cause: Grid W-U line voltage below the protection setting, or AC cables not firmly and correctly connected.

How to fix it

Check the AC voltage protection setting; check the voltage difference between the LCD and a meter; check that all AC cables are firmly and correctly connected.

Source: 063_BManual_SUN-6K-G06-LV-P1_20250923_en_30a96699.pdf, p.58 · 031_BManual_SUN-1_1.5_2_2.2_2.5_2.7_3_3.3_3.6_4K-G04P1-EU-AM1_20260624_en_15adc00c.pdf, p.54 · 036_BManual_SUN-3_4_5_6_7_8_9_10_12_15K-G06P3-EU-BM2_20250506_en_0eb78440.pdf, p.58

Also applies to:SUN-3.6K-SG05LP1-EU-SM2-PSUN-5K-SG05LP1-EU-SM2-PSUN-6K-SG05LP1-EU-SM2-PSUN-7K-SG05LP1-EU-SM2-PSUN-7.6K-SG05LP1-EU-SM2-PSUN-8K-SG05LP1-EU-SM2-PSUN-10K-SG05LP1-EU-SM2-PSUN-7.6K-SG01LP1-EU+21

What it means

AC line low voltageGrid voltage fault: the AC line voltage is out of the permitted range.

Cause: The grid AC voltage is outside the standard voltage range in the specification, or the grid AC cables are not firmly and correctly connected.

How to fix it

  1. Check that the AC voltage is in the range of the standard voltage in the specification and that the grid AC cables are firmly and correctly connected.
  2. Seek help from Deye if the inverter cannot go back to the normal state.

Source: 039_BManual_SUN-3.6_5_6_7_7.6_8_10K-SG05LP1-EU-SM2-P_20260428_en_70c401a6.pdf, p.50 · 043_BManual_SUN-12_14_16K-SG01LP1-EU_20260519_en_703e15ac.pdf, p.46 · 052_BManual_SUN-_3.6-6_K-OG01LP1-EU-AM2_20260406_en_dc31b173.pdf, p.46 · +4 more official manuals

Also applies to:SUN-5K-SG01HP3-EU-AM2SUN-6K-SG01HP3-EU-AM2SUN-8K-SG01HP3-EU-AM2SUN-10K-SG01HP3-EU-AM2SUN-12K-SG01HP3-EU-AM2SUN-15K-SG01HP3-EU-AM2SUN-20K-SG01HP3-EU-AM2SUN-25K-SG01HP3-EU-AM2+9

What it means

Parallel Version FaultParallel_Version_Fault - the firmware versions of the paralleled inverters do not match.

Cause: The software/firmware versions of the inverters connected in parallel are not consistent.

How to fix it

  1. Check whether the inverter versions are consistent
  2. Contact us to upgrade the software version.

Source: 037_BManual_SUN-5_6_8_10_12_15_20_25K-SG01HP3-EU-AM2_20260224_en_9ef2717c.pdf, p.51 · 050_BManual_SUN-29.9_30_35_40_50K-SG01HP3-EU-BM3_4_20260224_en_544e1b2f.pdf, p.52 · 062_BManual__SUN-60_70_75_80K-SG02HP3-EU-EM6_20260224_en_38cbc9f6.pdf, p.52

Also applies to:SUN-5K-SG02LP2-US-AM2SUN-6K-SG02LP2-US-AM2SUN-7.6K-SG02LP2-US-AM2SUN-8K-SG02LP2-US-AM2SUN-10K-SG02LP2-US-AM3SUN-12K-SG02LP2-US-AM3SUN-5K-SG04LP3-EUSUN-6K-SG04LP3-EU+15

What it means

AC Line Low VoltageAC line low voltage - grid voltage fault.

Cause: The grid AC line voltage is below the standard voltage range in the specification.

How to fix it

  1. Check that the AC voltage is in the range of the standard voltage in the specification
  2. Check whether the grid AC cables are firmly and correctly connected
  3. Seek help from us if it cannot go back to the normal state.

Source: 059_BManual_SUN-5_6_7.6_8_10_12K-SG02LP2-US-AM2_AM3_20260406_en_fb6a30c7.pdf, p.55 · 038_BManual_SUN-5_6_8_10_12K-SG04LP3-EU_20260319_en_081932c1.pdf, p.47 · 040_BManual_SUN-3_4_5_6_8_10_12K-SG05LP3-EU-SM2_20260319_en_b0183b7d.pdf, p.47 · +1 more official manuals

AI-W5.1 ESS

Energy storage systemFault

Also applies to:AI-W5.1-5P3-EU-B-ESSAI-W5.1-6P3-EU-B-ESSAI-W5.1-8P3-EU-B-ESSAI-W5.1-10P3-EU-B-ESSAI-W5.1-12P3-EU-B-ESS

What it means

AC line low voltageGrid voltage fault - AC line voltage out of range (low).

Cause: The grid AC voltage is outside (below) the standard voltage range in the specification, or the grid AC cables are loose or incorrectly connected.

How to fix it

  1. Check that the AC voltage is within the standard range and that the grid AC cables are firmly and correctly connected.
  2. Seek help from Deye if it does not recover.

Source: 002_Download_4e90fe7a.pdf, p.47

GB-SL / GB-SL Pro ESS

Energy storage systemFault

Also applies to:GB-SL5K-EUGB-SL6K-EUGB-SL8K-EUGB-SL10K-EUGB-SL12K-EUGB-SL15K-EUGB-SL20K-EUGB-SL Pro 5K-EU+6

What it means

Parallel_Version_FaultParallel firmware-version mismatch.

Cause: The firmware versions of the paralleled inverters are not consistent.

How to fix it

Check whether the inverter firmware versions are consistent and contact Deye to upgrade the software to matching versions.

Source: 081_deye_gb_sl_pro_user_manual_46fa941a.pdf, p.50 · 010_Download_cc05df18.pdf, p.45

GB-A HV Battery

BatteryFault

Also applies to:GB-A

What it means

ALARM_ID_CHG_RELAY_DRIVE_FAULTCharging relay drive failure.

Cause: The drive circuit for the charge relay failed - the relay cannot be actuated.

How to fix it

  1. Restart the system.
  2. If the fault persists, contact Deye support for service.

Source: 008_deye_ess_user_manual_gb_a_jpnen_v02_20250829_3fea617e.pdf, p.14

Frequently asked questions

What does error 42 mean on a DEYE inverter?
It depends on the model — 13 devices use code 42. On the SUN G01P3-EU-BM8 Series it means: AC Line W,U low voltage. The card for each model on this page gives its exact meaning and fix.
Is error 42 a fault or a warning?
42 is a fault code: the inverter cuts its output and the red LED stays solid until it is cleared.
How do I clear or fix error 42?
Check the AC voltage protection setting. Check the voltage difference between the LCD and a meter, and check whether all AC cables are firmly and correctly connected. The exact steps for each affected model are listed on this page.

Related error codes

Prefer the full written guide? Read the complete DEYE inverter error-code guide

Compiled from official DEYE user manuals. Always consult your device manual and a qualified technician before performing repairs.