A solar inverter that has stopped working is one of the most common calls we receive at Sunce Renewables. The good news: many causes are simple, and some can be checked safely without opening the inverter. Here are the nine causes we see most often, in roughly the order you should rule them out.
1. A breaker or isolator is switched off
Check the DC isolator next to the inverter and the AC breaker in your ACDB or distribution board. Maintenance staff, electricians or a tripped MCB often leave one of them off.
2. There is no grid supply (on-grid inverters)
On-grid inverters are designed to shut down when the grid fails. This is a safety feature called anti-islanding, not a fault. Generation resumes a few minutes after the grid returns.
3. Grid voltage is too high
If your site is at the end of a long feeder, grid voltage can exceed the inverter's limit around midday, causing it to disconnect repeatedly. The display usually shows a grid over-voltage error. This needs a check of the AC cable size and a discussion with the DISCOM — not an inverter replacement.
4. Isolation or earth fault on the DC side
Damaged DC cables, water in a junction box or a burnt MC4 connector reduce insulation resistance. The inverter refuses to start, especially on humid mornings, and shows an isolation or ISO error.
5. Overheating
Inverters in direct sun or with failed fans derate or shut down to protect themselves. If it stops in the afternoon and restarts in the evening, heat is a likely cause.
6. Blown fuses or a failed relay
String fuses, internal fuses and grid relays fail with age. A relay check failure error points directly at this.
7. Failed auxiliary power supply
If the display is completely blank even with good DC voltage in daylight, the inverter's internal power supply (SMPS) may have failed.
8. Control or power board failure
Lightning, surges and age can damage the control board or IGBT power stage. These need PCB-level repair in a workshop.
9. Configuration or firmware problems
Wrong grid code, country settings or a failed firmware update can stop an inverter from connecting. This is common on hybrid inverters.
What you can safely do
- Note down the exact error code or take a photo of the display
- Check the AC breaker and DC isolator positions
- Check whether the grid supply is available
- Look at the monitoring app for when generation stopped
- Do not open the inverter or disconnect DC cables under load — solar DC voltage is dangerous
Frequently asked questions
Why does my inverter show no generation even when it is sunny?
The inverter may be disconnected from the grid, have an isolation fault, or have tripped on high grid voltage. Check the display for an error code first.
Need a solar inverter repaired?
Share your inverter brand, model and error code — our technicians will guide you and share an estimate before any repair starts.