Top 10 most common technical failures and how to fix them 

Solar installations are sustainable and reliable, but like any technology, issues can occur. At ESTG, we’re happy to help you with practical solutions for the most common problems. These tips give you quick insights and actionable steps: 

1. Cable break or cable damage 

Issue:
No output from one or more strings, inverter error messages, abnormal voltage readings. 

Solution: 
Cable damage is a common issue in solar installations. It can be caused by kinks, breaks or even animal bites. Always start with a visual inspection of the cables. Look closely for damage and check MC4 connectors for corrosion or loose connections. Then test the cables using a continuity tester or multimeter to confirm the issue. Replace damaged cables immediately and always use UV-resistant, double-insulated cables to avoid future failures. 

2. Communication failure between inverter and monitoring portal 

Issue:
No data in the monitoring system, error messages like “No connection” or “Offline”. 

Solution: 
A disrupted connection between the inverter and the internet is a frequent issue in solar systems. First, check whether the internet connection is active, both via cable and Wi-Fi, and ensure the router is functioning correctly. If everything works, reset the inverter or data logger according to the manufacturer’s instructions. You may need to reconfigure the connection via ethernet or Wi-Fi. Don’t forget to check if the correct ports are open in the router settings for communication with monitoring platforms. 

3. Inverter failure or error code 

Issue:
Red LED, error messages like “Grid Fault”, “Isolation Fault” or “Overvoltage”. 

Solution: 
If the inverter shows an error code, first look it up in the manual for that specific model to understand what it means. Then check the grid voltage and grounding resistance, deviations here are often the cause. A reset or firmware update might fix the issue. If the problem persists or is a critical error, contact the manufacturer or consider replacing the inverter. 

4. Ground fault or insulation error 

Issue:
Inverter doesn’t start or displays “Insulation resistance low”. 

Solution: 
If there’s an insulation error, measure the insulation resistance between plus or minus and ground. This value must be at least 1 MΩ to operate safely and reliably. If the resistance is too low, inspect all panels and cables thoroughly for damage or moisture. This is especially common after heavy rain or in older systems. Replace defective components to prevent further damage or safety risks. 

5. Mismatch between solar panels and inverter 

Issue:
Low output, error code “Input voltage too low/high”. 

Solution: 
Incorrect string configuration can lead to performance loss or system faults. Always ensure the panel configuration stays within the inverter’s MPPT range. If not, adjust the number of panels per string to match the voltage and current to the inverter. Ideally, use a configuration tool like SolarEdge Designer or SMA Sunny Design to create an efficient and correct layout for maximum performance. 

6. Panel shading or contamination 

Issue:
Significantly reduced output, uneven string performance. 

Solution: 
If one or more panels are underperforming, use a monitoring tool to identify the affected string or panel. The issue is often dirt, like leaves or bird droppings, which can be removed manually. If shading is structural, consider investing in optimizers or microinverters. These ensure that shading on one panel doesn’t affect the entire system. 

7. Poor connection in MC4 connectors 

Issue:
Intermittent faults, high contact resistance. 

Solution: 
Connector issues are among the most underestimated causes of failures and power loss. Disconnect the MC4 connectors and inspect them for signs of burning or corrosion. A poor connection can generate heat and even pose a fire hazard. Always use original MC4 tools during installation to prevent damage or faulty connections. Not sure if a connector is still safe? Replace it to eliminate risk. If possible, perform a thermographic inspection to detect hotspots early and avoid major issues. 

8. Inverter shuts down due to grid voltage spikes 

Issue:
Frequent shutdowns on sunny days, messages like “Overvoltage Grid”. 

Solution: 
Grid overvoltage problems are increasingly common in sunny regions. Measure the grid voltage directly at the inverter. If spikes above 253V are detected, contact the grid operator. They can assess whether grid upgrades are needed. In some cases, reducing the AC cable diameter or adjusting inverter parameters may help, but only with approval and coordination from the grid operator. 

9. No synchronization with the grid 

Issue:
Inverter remains in “Waiting” or “Grid Monitoring” mode. 

Solution: 
For grid coupling issues, first check the grid frequency and voltage. If these are within acceptable limits, verify that the wiring is correctly connected: ensure L (live), N (neutral), and PE (ground) are in the right order. Secure all connections and restart the system correctly. Switch off the DC side first, then power up the AC side. This prevents errors and ensures safe startup. 

10. Outdated or incorrect inverter firmware 

Issue:
Unexplained error messages or poor communication. 

Solution: 
Firmware updates are essential for stable and secure inverter operation. Log into the manufacturer’s portal and check if the current firmware is up to date. If a new version is available, download and install it according to the instructions. For USB updates, make sure to use a FAT32-formatted stick and follow the correct folder structure. Unsure about how to proceed? It’s best to have a professional handle the update. 
 

Keep Your System in Top Condition 
Technical failures do happen, but with the right knowledge, they’re often easy to solve. This top 10 gives you practical tips and key checks. Want to be sure your installation stays safe and efficient? Get in touch with ESTG for advice or support. This way, your solar power system stays in top shape and you avoid unnecessary power loss!