Common Generator Failures & How to Address Them

Common Generator Failures & How to Address Them

October 30, 2017

Businesses rely on electric power to function. If power is disrupted, operations are interrupted and revenues are lost. Many companies are setting up their facilities with standby power in the form of generators, to protect the bottom line from being impacted by power disruptions.

But generators are complex machines, and they can fail. Facilities managers need to know the most common causes of failure and what to do when they occur.


Before you start digging in too deep, check for a “not in auto” message. A “not in auto” message will appear if the main control switch was left in the off/reset position after testing or servicing. After any service is performed on a unit, it’s a good idea to check that the generator is functioning properly.

However, “not in auto” may not actually refer to a problem with the main control switch. If an alarm hasn’t been reset, if breakers were left open, if switchgear was not reset, or if emergency stop buttons have been activated, the “not in auto” message will appear. Because of this, you may need to check several things. Different models will have different requirements, so you’ll want to refer to your owner’s manual.


Battery failure is the most common cause of a generator’s inability to start. And battery failure is most often due to sulfation buildup (lead sulfates accumulating on the plates of the batteries). When enough of the plate area has sulfated, the battery won’t be able to provide sufficient current. If your battery failure is the result of sulfation, you’ll need to replace the battery.

Batteries can also fail if the sedimentary trays fill up with lead debris. This problem is easily prevented by replacing the batteries every three years. Open cells, while not a common occurrence, can also cause battery failure. Open cells are the result of an overcurrent. Your unit may require larger batteries that are capable of higher cold cranking amps (CCAs).

Battery failure can also happen if the charger breaker is open or tripped. It’s a good idea to double check after any service or maintenance to make sure the charger was turned back on and that the generator is functioning properly.

Most battery problems can be prevented by maintenance that addresses loose or dirty connections. Cable connections should be cleaned and tightened regularly. Battery issues due to charger failures, while less common, are difficult to prevent. Monitoring the charge rates from month to month will help you map the potential for failure, so you can more accurately predict problems. If you see a constant charge rate, your battery charger is likely working properly. But an increase of amperage signals upcoming problems.


Oil leaks are often due to running the generator for extended periods of time with no (or very low) load. Diesel engine generators are designed to operate with a load, so when they operate significantly below the rated output level, the engine can start to over-fuel and cause damage to the engine. If you need your generator to run loads considerably below the rated output level, you can pair the generator with an automatic load bank, which will place a false load on the generator system.

Fuel leaks are commonly caused by overfilling the base tank. This can happen because of human error or a failure in the pump system. You’ll want to regularly check to make sure the remote tank pump systems and emergency shutoff systems are functioning properly, and also check the flexible fuel lines regularly to search for cracks or signs of wear.

Coolant leaks often occur in the block heater hoses. Extreme temperatures wear on the hoses — this is why silicon hoses are recommended for block heaters. You should install isolation ball valves for block heater hose connections, which, in combination with cooling system maintenance, should prevent most leaks. Always check for leaks during your regular inspections. Also check the hoses for a crusty substance that indicates seeping.


In addition to coolant leaks causing low coolant levels, internally-plugged radiator cores can cause low coolant levels. If the radiator is overloaded and doesn’t allow the proper amount of flow through the core, the coolant purges through the overflow line. When the engine cools, the level drops and activates the low coolant level shutdown. A full load test with an external load bank is the only reliable way to check a cooling system.


Newer generators that aren’t run on a regular basis will sometimes experience air in the fuel system. This problem is easily preventable by running the engine for five minutes or so during weekly inspections, to verify that the engine will start, that the air is cleared from the fuel system, and that the generator comes up to voltage and frequency.

LEL purchases and sells industrial generators from 50 kW and up. For information on any of our equipment services or talk with an equipment expert, please call 864-249-0943.

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