Common solar inverter error codes explained

Codes are grouped, not random

Every brand uses its own numbering, which is why searching a code by itself often returns nothing useful. Underneath the numbering, though, almost every fault falls into one of six families. Identify the family and you already know roughly what happens next.

• Grid faults. Voltage, frequency, or grid loss. The inverter is protecting itself and the LESCO line. Usually not the inverter's fault.
• DC input faults. Over-voltage, under-voltage, reverse polarity, string imbalance. Points at the array or the wiring.
• Insulation and ground faults. Leakage to earth. Water, damaged cable, or missing earthing.
• Thermal faults. Over-temperature and derating. Placement and ventilation.
• Battery and communication faults. BMS handshake, over-voltage, over-current on the storage side.
• Internal hardware faults. Relay, bus voltage, DSP, EEPROM. The only family that genuinely means the unit needs opening.

The rest of this page walks family by family, with the codes each brand uses.

Grid fault codes

The most common family in Lahore by a wide margin, and the one most often misdiagnosed as an inverter defect.

Family	Inverex	Solis	SolarMax / Growatt	Meaning
Grid over-voltage	F03 / OVER GRID	G01 or AC-OV	Error 03 / Vac Fault	LESCO line above the allowed limit, often afternoon
Grid under-voltage	F04	G02	Error 04	Line sag during evening peak or a weak feeder
Grid frequency out of range	F05 / F06	G03 or G04	Error 05 / Fac Fault	Frequency drift, common right after an outage restores
Grid loss	F07 / NO UTILITY	G05 or NO-GRID	Error 07 / Utility Loss	Supply gone. Normal during load shedding
Anti-islanding trip	F09	G06	Error 09	Inverter detected an unsafe grid condition and isolated

Grid loss during load shedding needs no action at all on an on-grid build, the system simply waits. On a hybrid the battery takes over. If grid over-voltage repeats every clear afternoon, the fix is not the inverter: it is either the grid voltage window setting, an undersized AC cable run adding voltage rise, or a genuinely high feeder that LESCO needs to address. Homes clustered together in Wapda Town and newer Bahria Town blocks see this most.

DC input fault codes

These point at the roof, the strings, and the cable between them and the inverter.

Family	Inverex	Solis	SolarMax / Growatt	Where to look
PV over-voltage	F12 / PV OVP	DC-OV or 1010	Error 02 / PV Volt High	Too many panels per string, worst on cold January mornings
PV under-voltage	F13	DC-UV	PV Volt Low	Blown string fuse, open connector, or simply dawn
Reverse polarity	F14	DC-REV	PV Reverse	String wired backwards, almost always a fresh install error
Input over-current	F15	DC-OC	Error 06	Parallel strings mismatched or a shorted MC4
String current imbalance	Warning only	String alarm	String Warning	Shading, dirt, or one dead panel on a string

PV over-voltage on a January morning is worth explaining, because it surprises people. Panel open circuit voltage rises as temperature falls. A string designed at the edge of the inverter's limit during a 40C summer commissioning can exceed that limit at 4C in January, and the inverter refuses to start until the sun warms things up. This is a design error from the original install, not a component failure, and the fix is restringing.

Insulation and ground fault codes

Inverex shows F23 or F24, Solis shows ISO or 1017, SolarMax and Growatt usually give a PV ISO Low or GFCI message. All of them mean the same thing: the DC side has developed a leakage path to earth below the safe resistance threshold.

In Lahore these codes have a season. They appear during and after monsoon rain and clear on a dry week, which makes them frustrating to chase. The usual sources:

1. Water in a roof junction box, typically one mounted with cable glands facing upward or sealed with silicone instead of a proper gland.
2. DC cable insulation damaged where it crosses a sharp parapet edge without a conduit, then sitting in a puddle.
3. Rodent damage exposing conductor, which only trips the sensor once the roof is wet.
4. Missing or corroded earthing. A surprising number of Lahore installs have an earth wire terminated to nothing, or bonded to the house neutral, which is wrong and unsafe.

Do not keep resetting an isolation fault. It is one of the two genuine safety codes on this page. Get it traced with an insulation tester, string by string, and get the earthing checked while the technician is there. This is standard on any repair visit.

Thermal and derating codes

Over-temperature codes are OT or F18 on Inverex, TEMP-FAULT or 1011 on Solis, and Over Temperature on Growatt and SolarMax. Alongside them most brands log a fan fault code separately.

A derating message is not an error. It means the inverter is deliberately reducing output to keep its own components inside spec, which is exactly what it should do at 46C ambient. What matters is how early it starts. A wall-mounted unit in shade with clearance might derate for forty minutes on the hottest June afternoon. The same unit in a closed store room derates from noon and costs real units every day. The full placement argument sits in inverter overheating in Lahore summer.

A fan fault code is cheap to fix and expensive to ignore. Dust in Lahore kills inverter fans in three to four years. A replacement fan module runs PKR 4,500 to 8,000, against PKR 165,000 for a new 5kW hybrid.

Battery and communication codes on hybrids

Hybrid builds add a whole second set of codes on the storage side. These are the ones that come up most:

• BMS communication fail. The RJ45 between pack and inverter is loose, has the wrong pinout, or the battery protocol is set incorrectly in the inverter menu. Extremely common after adding a second module.
• Battery over-voltage. Almost always a charge profile left on lead acid settings after a lithium upgrade.
• Battery under-voltage or low SOC shutdown. The pack hit its floor. Normal after a long outage, a problem if it happens nightly.
• Battery over-temperature. Lahore summer, poor placement. Covered in battery not charging.
• Battery not detected. DC breaker between pack and inverter is open, or the pack's own isolator is off.
• Battery reverse polarity. Install error. Do not attempt a reset, disconnect and call someone.

Brand-specific behaviour differs a lot here. Pylontech and Dyness packs are generally well supported by Lahore-sold inverters. Some locally assembled packs advertise compatibility that does not fully work, and those installs end up running in voltage-only mode with no real communication, which hides genuine faults until something fails.

Internal hardware codes

Relay fault, bus over-voltage, DSP fault, EEPROM fault, and current sensor fault all sit in this family. Inverex numbers them in the F30s and F40s, Solis uses codes in the 1030 and 1040 range, and Growatt and SolarMax spell them out in words.

These are the ones that usually mean an authorised service centre. One full power cycle is worth trying, in the correct order: AC breaker off, DC isolator beside the inverter off, roof isolator off, wait five minutes, then reverse the order to restart. If the code returns immediately, stop.

Repair versus replace comes down to age and quote. Board-level work runs PKR 18,000 to 45,000. New units today are PKR 95,000 for a 3kW hybrid, PKR 165,000 for 5kW, PKR 158,000 for 6kW, and PKR 295,000 for 10kW. A repair quote above roughly 40 percent of replacement on a unit already five years old is not good money. Service reality by brand is discussed in the pages for Inverex, SolarMax, Solis and Huawei.

Reading fault history instead of chasing one code

A single code caught by eye tells you less than the log. Every modern inverter stores fault history with timestamps, and the app usually exposes it. Look for pattern rather than instance.

Grid codes clustered between 1 pm and 4 pm point at feeder over-voltage. Isolation codes clustered in July and August point at water. Thermal codes that begin earlier each week through May point at a fan that is dying. Battery communication codes that appear right after a firmware update point at a protocol mismatch. That pattern is worth more than any single screenshot.

Honest limitation: some cheaper units sold in Lahore keep only the last five faults and drop the rest, and a few clear the log on power cycle. On those, a technician has to leave a logger for a week to catch an intermittent fault. There is no way around that and anyone claiming otherwise has not done the work.

When a code costs more than the repair

An inverter sitting on a fault for a month is a month of buying every unit from LESCO at PKR 48 to 65. On a 10 marla home in Johar Town or Model Town running two ACs in summer, that is easily PKR 25,000 to 40,000 of avoidable bill, often several times the cost of the fix.

If the system is on net metering, the meter also stops crediting exports during that period, so the loss stacks. Getting a code looked at in week one is simply cheaper. Broader cost context sits in solar repair costs, your LESCO bill after solar, and if the system turns out to be undersized rather than faulty, the calculator and the installation team.