Your inverter has detected an insulation fault and shut down as a safety measure. Work through this diagnostic guide to identify the cause. Most cases can be narrowed down remotely, and we can advise on whether a site visit is required.
Book your free remote diagnosticHow to safely shut downSafety: Isolate the system at the consumer unit. Do not restart or override the fault.
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Error 04 has four main root causes. Work through these steps in order to narrow down which is affecting your system.
Error 04 is a safety fault. Switch off the main AC isolator at your consumer unit and the DC string isolator near the roof-mounted array. Do not touch any DC connections on the roof. Do not repeatedly restart the inverter in an attempt to clear the fault — this will not fix it and only risks exposure to live voltage.
Log into ShineServer and navigate to Fault Logs. Note the exact date and time Error 04 first appeared. Check the weather on that date — if it appeared in the morning during wet or rainy weather, MC4 connector water ingress is almost certainly the cause. If it appeared after weeks of dry weather, a gradual cable or panel degradation is more likely.
This step requires safe roof access. Inspect all MC4 connectors between the solar panels and the inverter. Look for: water droplets visible inside the connector housing, corrosion or whitish crystalline deposits, discoloured or corroded connector pins, or physical cracking of the connector body. Pre-2018 installations are most vulnerable — connectors degrade and lose weatherproofing over time. If you see water ingress, the connector must be replaced.
Check the DC cable that runs from the roof array down to the inverter. Look for: cracks or splits in the cable insulation (often appear as fine white lines from UV exposure), physical damage from installation work or weather, crushed sections, or discolouration. Damaged cable insulation is the second most common Error 04 cause. Check the full cable run from roof to inverter.
A failed or cracked junction box on a specific panel can cause localized insulation loss. If you can safely view the back of the panels (during a site visit), inspect the junction boxes for visible cracks, discolouration, or separation from the panel. A single faulty panel can often be isolated from the string by repositioning the string combiner input.
After the fault source is identified and repaired, a qualified engineer must perform an insulation resistance (IR) test on the DC string. Resistance must be ≥1MΩ as required by BS EN 62446-1 via BS 7671 Section 712 before the system can be safely restarted. Do not restart the inverter without documented IR test results.
Owners and installers write this one several ways: Error 04, Error 4 without the leading zero, error code 04, or fault 04. They all refer to the same isolation fault described on this page.
Inverter screen shows "Error 04" with a red LED indicator. The system stops generating and feeding to grid.
Log into ShineServer → Device → History. Filter by date and look for "Error 04" entries with timestamps.
Error history tab shows recent faults including Error 04 with timestamp.
SPH-TL-BH series — hybrid inverters with battery
MIN-TL-X series — single and three-phase string inverters
MOD-TL3-X series — three-phase string inverters
ShineMaster range — older models with insulation monitoring
Replace the water-damaged connector pair. Quick fix if the fault is isolated to one connector.
Replace the damaged section of DC string cable. Cost depends on cable run length and roof access.
Cracked or failed junction box requires panel replacement. May be covered under panel warranty.
Repeated power cycles do not clear insulation faults. Each restart attempt increases stress on degraded components and may worsen the underlying issue.
DC circuits carry lethal voltage even when the inverter is off. Water ingress or damaged insulation create shock hazards. Only a qualified engineer should inspect DC wiring.
Insulation faults caused by moisture or damage are progressive — they worsen over time. A fault that appears occasionally will eventually become permanent.
Error 04 is the most common Growatt fault code in the UK, particularly on installations from 2015–2022. It affects SPH, MIN, MOD, and older ShineMaster models equally. The inverter detects DC insulation resistance falling below 1MΩ (the BS EN 62446-1 test threshold, applied through BS 7671 Section 712) and disconnects as a safety measure. This is not a Growatt hardware fault — it is almost always external to the inverter, indicating either connector degradation, cable damage, or a failed panel junction box.
ShineServer logs the exact time the fault appeared, allowing correlation with weather events. Morning appearance in wet weather almost always points to MC4 connector water ingress. Older installations on original equipment are most vulnerable due to connector age.
Tell us what's happening. We'll review your ShineServer data and fault logs to diagnose the cause remotely — most cases are narrowed down in a single session.
Due to unprecedented demand we’re currently only carrying out on-site work in Yorkshire, and replies are taking up to 7 days. Remote diagnostics continue for the whole UK as normal.
Every message is read and answered, so please don’t send it twice; that only slows the queue.
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