Solar systems are among the most reliable power generation technologies available — but when something goes wrong, a non-producing system is a silent cost every hour it's down. Over hundreds of installations across Tamil Nadu, we've seen every failure mode imaginable. This guide gives you a structured way to diagnose the most common problems, understand what's safe to check yourself, and know when to stop and call a certified technician.

Safety Warning: All DC solar circuits carry high voltage — typically 300–600V DC for residential string systems, up to 1000V DC for commercial installations. DC current does not cross zero like AC, making arc faults particularly dangerous. Never open combiner boxes, disconnect DC wiring, or probe DC conductors without proper isolation and safety equipment. When in doubt, stop and call a professional.

Diagnostic Flowchart

Before diving into specific problems, follow this sequence:

System not generating?
  │
  ├─ Check inverter display → Error code shown?
  │     ├─ YES → See error code table below
  │     └─ NO display at all → Check AC isolator, main breaker, grid supply
  │
  ├─ Inverter shows normal but low output?
  │     ├─ Check weather conditions first (cloud cover?)
  │     ├─ Check panel surface (soiling, shading?)
  │     └─ Compare to same-day baseline from inverter history
  │
  └─ Output recently dropped and weather is fine?
        ├─ Inspect panels visually (shading, soiling, damage)
        ├─ Check all isolators and breakers
        └─ Call technician if no obvious cause found

Problem 1: Zero Output — System Not Producing at All

Symptoms: Inverter display dark or showing "Standby." Generation data shows 0 kWh for the day despite sunshine.

Step-by-step diagnosis:

Check the AC isolator switch between inverter and distribution board — verify it's in the ON position. This is the most common cause of sudden zero output after maintenance or a power cut.
Check the main household circuit breaker — a tripped breaker on the solar circuit cuts inverter output.
Check grid supply — on-grid inverters shut down when grid power is absent (anti-islanding protection). Confirm TANGEDCO supply is present at your meter.
Check the DC isolator switch at the inverter — confirm it's ON.
Look at the inverter display — note any error code displayed and cross-reference below.
Check inverter LED indicators: Green = normal, Amber = warning, Red = fault.

If all switches are on and grid is present but inverter is dark: The inverter may have lost power to its control board. Try switching the AC and DC isolators off, waiting 2 minutes, and restarting. If no recovery, call a technician.

Problem 2: Low Output — System Producing but Below Expected

Symptoms: System generates power but consistently 20–40% below expected seasonal baseline on clear days.

Common causes and checks:

Soiling: A thin layer of red dust cuts output by 8–15% in Tamil Nadu's dry season. Clean panels thoroughly and recheck.
Partial shading: A new obstruction — a freshly grown tree branch, a newly installed water tank, a neighbour's construction — can shade one or more panels. Even partial shade on a single panel can reduce an entire string's output. Walk the roof and observe shadows at solar noon (approximately 12:30–1:00 PM IST).
Panel degradation: If the system is 7+ years old, check your historical generation records. A gradual multi-year decline of 0.5–0.7%/year is normal. A sudden step-down suggests a failed cell or string.
MPPT mismatch: If panels of different wattages or orientations were mixed on the same MPPT input during installation, output will be limited to the weakest panel in the string.
Inverter MPPT range mismatch: If string voltage sits outside the inverter's MPPT voltage window (check datasheet), the inverter harvests less than available.

Problem 3: Inverter Not Connecting to Grid

Symptoms: Inverter displays "Grid Fault," "No Grid," or "Waiting for Grid." Error persists beyond 5 minutes.

Causes and solutions:

TANGEDCO grid voltage out of range: TANGEDCO voltage fluctuations are common, especially during evening peak demand. Inverters are set to disconnect when voltage exceeds ~253V or drops below ~180V (per CEA regulations). Wait 10–15 minutes and check again. If the problem recurs daily, consider a grid voltage monitor.
Anti-islanding protection: This is a safety feature — when grid power is interrupted, the inverter disconnects within milliseconds. It will reconnect automatically once stable grid power is restored.
Net meter wiring issue: If TANGEDCO recently changed your meter or performed work on your connection, verify the meter is correctly wired for net metering (bidirectional). An improperly wired net meter can prevent the inverter from seeing a stable grid reference.
AC cable fault: Check that the AC output cable from inverter to distribution board is intact and properly terminated.

Problem 4: Inverter Error Codes

Common error codes across widely-used inverters in Tamil Nadu:

Inverter Brand	Error Code	Meaning	Action
Growatt	Fault 14	Ground fault / insulation failure	Call technician — do not reset
Growatt	Fault 22	Grid over-voltage	Check TANGEDCO voltage; wait
Growatt	Fault 24	Grid frequency out of range	Grid issue — wait for recovery
Deye/Sunsynk	E027	Inverter over-temperature	Clear ventilation; check fan
Deye/Sunsynk	E029	Bus voltage high	String voltage issue; call technician
Solis	F34	Ground fault detected	Call technician — do not reset
Solis	F15	Grid voltage protection	TANGEDCO voltage issue
Fronius	567	Arc fault detected	Call technician immediately

For any code not listed here, search "[inverter brand] error code [number]" in the manufacturer's portal or call your installer.

Problem 5: Ground Fault Detected

Symptoms: Inverter displays "Ground Fault," "Isolation Fault," or "Insulation Failure." Generation stops immediately.

What it means: The DC insulation between a live conductor and earth has broken down. This is often caused by:

Moisture ingress into a junction box or MC4 connector
Rodent damage to DC cable insulation
Pinched cable where it passes through metal conduit edges
Aged or UV-degraded cable in older systems

Action: Do not reset and ignore. A persistent ground fault is both a fire risk and a safety hazard. Switch off the DC isolator and AC isolator and call a certified solar technician for insulation resistance (IR) testing with a megohmmeter to locate the fault.

Problem 6: Battery Not Charging (Hybrid/Off-Grid Systems)

Symptoms: Battery State of Charge (SoC) stays low or does not rise despite sunshine. Battery voltage not increasing through the day.

Diagnostic steps:

Check inverter battery charging settings — confirm charging current limit, absorption voltage, and float voltage are set per your battery manufacturer's specification.
BMS communication fault: Lithium battery packs communicate with the inverter via CAN or RS485. A disconnected communication cable causes the inverter to default to safe low-charge behaviour or stop charging altogether. Reconnect the BMS communication cable.
Cell imbalance (lithium batteries): If one cell group within the battery pack has significantly lower voltage, the BMS will prevent charging to protect the pack. This requires a battery specialist to diagnose and resolve.
Battery temperature cutoff: Most lithium BMS units cut off charging above 45°C and below 5°C. In Coimbatore's summer heat, a battery installed in an unventilated space will regularly hit thermal cutoff. Ensure adequate ventilation.
Lead-acid batteries: Check electrolyte levels (for flooded types), check for sulphation (voltage won't rise above 12.4V under load), and check for dead cells.

Problem 7: High Inverter Temperature — Thermal Shutdown

Symptoms: Inverter output power suddenly reduces at peak afternoon hours. "Over-temperature" warning in app. Fan audible at high speed before shutdown.

Solutions:

Ensure minimum 20 cm clearance on all sides of the inverter (check manufacturer specification)
Inverters must not be mounted in direct sunlight — mount in shade or indoors
Clean the inverter's cooling fins and fan vents — dust accumulation in Tamil Nadu can choke airflow within months
If the fan has failed (audible rattling or no airflow), replace it — this is a common consumable
For wall-mounted inverters in electrical rooms, ensure the room itself has ventilation; rooms reaching 45–50°C in summer cause repeated thermal trips

Problem 8: Fluctuating or Erratic Output

Symptoms: Generation data shows erratic spikes and drops even on clear days. AC output power fluctuates when checked with a clamp meter.

Likely causes:

Loose MC4 connectors: Thermal cycling causes connectors to expand and contract, eventually loosening. Loose DC connectors cause arcing, which appears as rapid fluctuation. Arcing in DC circuits is a fire risk — investigate urgently.
Micro-cracks in panels: Invisible to the naked eye but cause intermittent cell disconnection. Confirmed with electroluminescence (EL) imaging.
Loose AC terminal in inverter: Have a technician check torque on all AC output terminals.
Grid voltage instability: Check TANGEDCO supply voltage — if it fluctuates between 200V and 250V rapidly, the inverter output will follow.

Problem 9: TANGEDCO Net Meter Reading Issues

Symptoms: Net meter appears to count only import units, not export. Monthly bill shows no solar credit. Meter reading doesn't match inverter export data.

Checks:

Confirm the meter installed is a bidirectional (net) meter — it should display both import and export registers separately. Single-direction meters cannot count solar exports.
Verify the meter's CT polarity — a reversed CT will show zero export or negative import. This requires a TANGEDCO junior engineer to verify.
Compare the inverter's cumulative export (kWh) with the meter's export register. Large discrepancies (>5%) should be formally raised with TANGEDCO through a written complaint at your local section office.
If your net meter was installed more than 3 years ago, request a meter accuracy test — TANGEDCO is required to test meters on consumer request.

Problem 10: App Not Showing Real-Time Data

Symptoms: Inverter functioning normally (lights green, generating power) but the monitoring app shows "offline," "no connection," or stale data.

Solutions:

WiFi dongle disconnected: Check the monitoring dongle (typically a small USB or plug-in module attached to the inverter) — reseat it firmly.
WiFi network changed: If your home router password or SSID changed, re-pair the dongle to the new network using the manufacturer's app setup process.
Router too far from inverter: Solar inverters are often installed in electrical rooms far from the router. WiFi signal below -70 dBm causes frequent dropouts. Consider a WiFi range extender near the inverter.
RS485 data logger issue (commercial systems): Restart the data logger and check the RS485 cable termination at both ends.
Cloud server outage: Rare but possible — check the manufacturer's service status page before extensive troubleshooting.

When to Call a Certified Technician vs DIY Fix

Issue	Safe for Owner	Requires Technician
Cleaning panels	Yes	No
Restarting inverter (AC/DC off, wait, restart)	Yes	No
Checking and resetting tripped AC breaker	Yes	No
Reconnecting WiFi dongle	Yes	No
Opening DC junction boxes or combiner box	No	Yes
Any ground fault or arc fault code	No	Yes
Replacing MC4 connectors	No	Yes
Checking earthing continuity	No	Yes
Testing panel IV curves	No	Yes
Physical damage to panels or cables	No	Yes

Tristar Green Energy Solutions in Coimbatore provides rapid-response fault diagnosis and repair services for solar systems across Tamil Nadu. Our MNRE-certified technicians carry IR cameras, megohm testers, and IV curve tracers for comprehensive diagnostics. If your system isn't performing as it should, contact us — most issues can be diagnosed and resolved within 24–48 hours.

Troubleshooting Common Solar System Issues