What Does The Fault Light Mean On A Power Inverter?

Power Inverters are designed to convert direct current (DC) from a battery or a solar panel array to alternating current (AC) in AC-powered applications.

Most power inverters are fitted with some visual and audible indicators to communicate the operational state of the inverter. Inverters typically have a “Green” light to indicate that it is ON and a “Red” light to indicate a problem. The audible sound of the cooling fans running is another cue.

The inverter lights indicator table below shows the various operating conditions and the indicator lights and cooling fan status.

Inverter Lights And Audible IndicatorsGreen LightRed LightCooling Fans
Normal OperationONOFFRUNNING
Low Solar ConditionsIntermittentOFFOFF
Temperature Too HighOFFONRUNNING
Inverter Light and Their Meanings

Let’s look at all the possible conditions that may lead to the Red light to indicate a problem.

Why Is The Red Light On The Inverter On?

After switching the inverter on, the “Red” light illuminates, but the “Green” light stays off, and the cooling fan does not run. One of the following DC Input conditions may exist:

  1. A short circuit exists to the inverter, and the Red light indicates that the overcurrent protection is active. Check that the cables connecting the DC input are not touching and causing a short circuit or are poorly connected.
  2. The input voltage from the battery bank or the solar array is either too low or too high, and thus the Red light indicates that the low current and overcurrent protection is active. Check that the DC input power voltage is within the specified operational range.
  3. If the inverter is switched on initially, the Greenlight goes off, and the Red light comes on, but the cooling fan stops running as soon as the AC loads are connected, indicating an AC Load problem.

The total AC load connected to the inverter exceeds the rated output capacity of the inverter, and the overload protection has been enabled. Disconnect all the AC loads from the inverter and check that the total load connected is less than 80% of the maximum operational output rating of the inverter.

  1. The AC output may be short-circuited due to wiring or a faulty appliance, and the overload protection has been enabled. Check for faulty appliances and disconnect them or short circuit conditions in the cabling.
  2. The inductive load of the inverter has been exceeded. Electrical motors in some appliances require a short surge of power when the motor starts up. Check the Surge Rating of the inverter and only connect appliances that do not exceed this inductive load.
  3. The inverter is switched ON and runs for a while before the Red light illuminates, and the fan stops running. The problem may be on the AC output or the DC input side of the inverter.

The AC output is short-circuited due to a faulty appliance or wiring problem, and the overload protection is enabled. Check for short circuits in the wiring, unplug the AC loads, and test each for proper functioning.

  1. The DC input voltage may be too low due to the state of discharge from the battery or insufficient sunlight on the solar panels. The inverter has enabled low voltage protection. Check the battery state of charge and recharge as required. Wait for the sunlight to strengthen sufficiently.
  2. The DC input voltage may be too high cold excessive power generation of the solar panels during cold conditions. The inverter has enabled high voltage overload protection. Check the solar panel DC output voltage. Your inverter watt rating is too small to cope with cold conditions overproduction.

What Are Some Green Light Problem Conditions On Inverters?

The inverter is switched on and has been running for some time. The “Green” light is illuminated, but the cooling fans are generating excessive noise.

  1. Noise from the inverter cooling fans will increase as the inverter components heat up under operating conditions. If the condition persists, the inverter may overheat, and the Red light will illuminate as the inverter shuts down.

Reduce some of the AC loads on the inverter to reduce the workload. An inverter should only be loaded to 80% of its rated operating capacity.

  1. After the inverter has been running for some time and operating as normal, the Greenlight goes OFF, the Red light stays OFF, and the cooling fans stop running. The problem may be on the DC input or inside the inverter.

To check for the DC input, use a multi-meter to measure the DC input voltage from the battery or the solar panels. The battery may be discharged too deeply and is damaged, or the sunlight intensity is too low.

  1. The components inside the inverter may be damaged. Check for short circuit conditions or a blown fuse. If neither of these conditions exists, the inverter is defective and must be repaired or replaced.

Most modern inverters are also fitted with an LCD that may provide you with error codes that will explain a Red light condition. Alarms are also audible and repetitive to ensure that the issue is attended to before the problem can escalate in severity.

Do not let audible or visual alarms go unattended as the consequences could be an expensive repair or replacement of the inverter. Inverters are designed to protect both the DC input side of the AC output appliances from damage.

The cost of a solar array or a battery bank will far exceed the cost of the inverter, and thus the inverter is seen as the sacrificial component in the system. Inverters will typically last about ten years before they need an extensive repair or replacement.

The inverter is also designed to protect the downstream AC appliances and devices from damage and will shut down or fail before damage is done. Inverters need to be regularly checked that their cooling fans are operational and not obstructed by dirt or debris.

The inverter should be installed in a well-ventilated, cool, and dry place that will detect visible and audible alarms. Don’t install them in places that are hard to access, as this will prevent you from doing frequent checks and maintenance.


See also: Solar Inverter Problems and Solutions: A Comprehensive Guide to Troubleshooting Common Issues

Photo of author
Elliot has 20+ years of experience in renewable technology, from conservation to efficient living. His passion is to help others achieve independent off-grid living.

SolVoltaics is an affiliate and an Amazon Associate, we earn from qualifying purchases - at no extra cost to you.