Generac Under Voltage Error Code 1902: Troubleshooting Guide

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Did you know that power outages cost the U.S. economy an estimated $150 billion per year? That’s why many people invest in a Generac generator to provide backup power for their home or business.

But what if your Generac generator fails to deliver the voltage you need? What if you see a red light flashing and an error code of 1902 on the generator’s control panel? What does that mean? And more importantly, how do you fix it?

The error code 1902 indicates an under-voltage condition. This means that the generator is not producing enough voltage to power your appliances or devices. This can be a serious and costly problem, as it can damage your generator and your electrical equipment.

In this blog post, I will explain what causes this error, how to troubleshoot it, and how to prevent it from happening again.

More articles on Generator Hacks to help you fix your Generac generator showing under voltage error code 1902.

What Causes Generac Under Voltage Error Code 1902?

Generac under voltage error code 1902

The most common cause of the voltage error code 1902 is a faulty voltage regulator. The voltage regulator is a device that controls the output voltage of the generator by adjusting the current to the rotor. If the voltage regulator is defective, it may not be able to maintain the correct voltage level, resulting in an undervoltage.

Another possible cause of undervoltage error code 1902 is a loose or corroded connection in the wiring or terminals of the generator. This can create resistance and reduce the voltage output. A dirty or worn-out air filter can also cause undervoltage, as it can restrict the airflow to the engine and affect its performance.

Other possible causes of the voltage error code 1902 include:

  • A mismatch between the generator’s frequency and the load’s frequency can create a power imbalance and affect the voltage output.
  • A short circuit or a ground fault in the wiring or the load can draw excessive current and lower the voltage output.
  • A high ambient temperature or a low coolant level can cause the generator to overheat and reduce its performance.
  • Overloading occurs when the total power demand of the appliances and devices connected to the generator exceeds the generator’s capacity. This can cause the generator to struggle to maintain the required voltage output and trigger the error code.

How do I troubleshoot Generac under Voltage Error Code 1902?

The first step to troubleshooting under voltage error code 1902 is to check the voltage output of the generator using a multimeter. You can do this by connecting the multimeter probes to the output terminals of the generator and measuring the AC voltage. The normal voltage range for a Generac generator is 220-240 volts. If the voltage is below this range, you have an under-voltage condition.

The next step is to inspect the wiring and terminals of the generator for any signs of damage, corrosion, or looseness. You can use a wire brush or a contact cleaner to clean the terminals and ensure a good connection. You should also check the air filter and replace it if it is dirty or clogged.

If the wiring, terminals, and air filter are in good condition, the most likely culprit is the voltage regulator. You can test the voltage regulator by disconnecting it from the generator and measuring the resistance between its terminals using a multimeter. The resistance should be between 20 and 30 ohms. If the resistance is too high or too low, the voltage regulator is faulty and needs to be replaced.

Another component that can affect the voltage output is the governor control. The governor control is a system that regulates the speed of the generator’s engine by adjusting the fuel supply. If the governor control is not working properly, it can cause the generator to run too fast or too slowly, resulting in under-voltage or over-voltage errors.

You can check the governor control by observing the engine speed and listening for any unusual noises. If the engine speed is erratic or the generator makes a rattling or knocking sound, the governor control may be malfunctioning and need to be adjusted or replaced.

Another condition that can cause a voltage error code of 1902 is speed. Underspeed is a condition where the generator is running at a lower speed than optimal, which can cause undervoltage. Underspeed can be caused by various factors, such as low fuel pressure, dirty filters, faulty spark plugs, or worn-out engine parts. 

You can diagnose underspeed by checking the fuel level and quality, the spark plugs and wires, and the engine oil and filter. You should also inspect the engine for any signs of wear and tear, such as cracks, leaks, or corrosion. If you find any problems, you should fix them or replace the parts as soon as possible.

How to Prevent Generac Under Voltage Error Code 1902?

The best way to prevent under-voltage error code 1902 is to perform regular maintenance on your Generac generator. You should follow the manufacturer’s recommendations for changing the oil, spark plugs, and filters, as well as cleaning and lubricating the generator parts. You should also run the generator at least once a month for 20 minutes to keep the battery charged and the engine in good shape.

Another way to prevent under-voltage error code 1902 is to avoid overloading the generator. You should always check the power rating of your appliances and devices and make sure that the total load does not exceed the generator’s capacity. You should also use a surge protector to protect your electrical equipment from voltage fluctuations.

How do I know if my generator is overloaded?

You can tell if your generator is overloaded by checking the following signs:

  • The generator’s circuit breaker trips frequently or continuously.
  • The generator’s output voltage drops below the normal range of 220-240 volts.
  • The generator’s output frequency deviates from the normal range of 50–60 Hz.
  • The generator makes loud or unusual noises, such as humming, buzzing, or clanking.
  • The generator emits smoke, sparks, or flames.

How do I reduce the load on my generator?

You can reduce the load on your generator by following these steps:

  • Turn off or unplug any appliances or devices that are not essential or in use.
  • Use energy-efficient appliances or devices that consume less power.
  • Use extension cords that are rated for the power and length required.
  • Distribute the load evenly among the generator’s outlets or circuits.
  • Avoid using appliances or devices that have high starting or surge power, such as air conditioners, refrigerators, or pumps.

You can learn more about reducing the load on your generator by reading this previous article we wrote here: How to Reduce the Voltage in a Generator.

How do I reset the error code 1902 on my generator?

You can reset the error code 1902 on your generator by following these steps:

  • Turn off the generator and disconnect it from the load.
  • Wait for at least 10 minutes for the generator to cool down.
  • Check and fix any problems that may have caused the error code, such as a faulty voltage regulator, the speed, loose wiring, a dirty air filter, or overloading.
  • Turn on the generator and reconnect it to the load.
  • Press the enter button on the generator’s control panel to clear the error code.
  • Lastly, reset the generator. You can learn how to reset Generac generators by reading this article here: How to reset Generac generators

Final Words

Generac under voltage error code 1902 is a common and serious problem that can affect your generator’s performance and lifespan. By following the steps above, you can diagnose and fix this problem and enjoy the benefits of your Generac generator. If you need more help or advice, you can contact a qualified Generac service technician.


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