Fixing Onan Generator - Troubleshoot Guide for Startup Issues

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Fixing Onan Generator - Troubleshoot Guide for Startup Issues

Table of Contents

  1. Introduction
  2. Basic Troubleshooting
    1. Checking for Nesting and Chewed Wires
    2. Start and Stop Issues
    3. Initial Checks
  3. Troubleshooting Guide
    1. Spark and Fuel Checks
    2. Holding the Start Button
    3. Unplugging the 12-Pin Connector
    4. Testing Voltages and Resistance
    5. Repairing Broken Links
    6. Issues with the Control Board
    7. Problems with the Regulator
  4. Free Troubleshooting Guide from Flight Systems
    1. Downloading the Guide
    2. Using the Guide as a Reference
  5. Conclusion
  6. Backup Generator Option
  7. The Convenience of Onboard Generators
  8. Pros and Cons
  9. FAQ

How to Troubleshoot Common Issues with Onan Generators


Onan generators are widely used for their power-producing capabilities. However, these generators are prone to certain issues that can disrupt their operation. In this article, we will discuss some of the common problems that Onan generators face and provide a step-by-step guide on how to troubleshoot and fix them.

Basic Troubleshooting

When encountering issues with your Onan generator, it is essential to start with basic troubleshooting steps. This section will cover two common problems and their corresponding solutions.

Checking for Nesting and Chewed Wires

Critters can create nests in various locations, including generator sets. These nests can cause damage to the wires and disrupt the generator's functionality. Before diving into comprehensive troubleshooting, it is advisable to check for any nesting or chewed wires. Cleaning out the nest and repairing any broken wires can potentially resolve the problem.

Start and Stop Issues

One of the most common problems Onan generators face is starting and stopping immediately after releasing the start button. If your generator starts and runs smoothly as long as you hold the start button, but shuts off when released, you may be dealing with this issue. Holding the button for a few seconds is safe and allows you to determine if the generator can sustain operation.

Troubleshooting Guide

For more complex issues, a comprehensive troubleshooting guide can help you diagnose and repair the problem effectively. This section will provide a step-by-step guide on how to troubleshoot your Onan generator, addressing various potential problems along the way.

Spark and Fuel Checks

Before delving into deeper troubleshooting steps, it is crucial to ensure the engine is ready to run. Check for spark in the spark plugs and verify if fuel is reaching the carburetor. These preliminary checks serve as the foundation for further troubleshooting.

Holding the Start Button

If your generator starts and continues running as long as you hold the start button, you can skip some of the initial checks. Ensure that the generator is in a running condition before proceeding with the troubleshooting process outlined in this guide.

Unplugging the 12-Pin Connector

To isolate the issue, it is necessary to unplug the 12-pin connector and use a multimeter to test for various voltages and resistances across different components. This step helps identify broken links and faulty connections, narrowing down the potential causes of the problem.

Repairing Broken Links

In some cases, the troubleshooting process may reveal broken links or intermittent connections in the control board. Repairing these broken links or replacing the control board can restore the generator's functionality. Following the guide's instructions and seeking assistance from a knowledgeable person can be beneficial during this step.

Issues with the Regulator

If the generator continues to exhibit irregular behavior, it may be necessary to investigate the regulator. The troubleshooting guide provides detailed instructions on how to diagnose and address any problems related to the regulator.

Free Troubleshooting Guide from Flight Systems

Flight Systems, a company based in Mechanicsburg, Pennsylvania, offers a free troubleshooting guide for Onan generators. The guide includes comprehensive information on troubleshooting procedures, testing voltages, and component resistance. It is available for download on the company's website, or it can be printed for easy reference during the troubleshooting process.

Downloading the Guide

To access the troubleshooting guide, visit the Flight Systems website and navigate to the section dedicated to Onan generators. There, you will find a link to download the guide as a PDF file. Having the guide on your desktop or in a printed format allows you to follow the troubleshooting steps conveniently.

Using the Guide as a Reference

The troubleshooting guide provided by Flight Systems is a valuable resource for those attempting to diagnose and repair their Onan generators. By referring to the guide's detailed instructions, you can potentially save money on labor costs and identify the faulty components accurately. Use the guide as a reference while working through each step of the troubleshooting process.


Onan generators are reliable power sources, but they can encounter problems that hinder their performance. By following a systematic troubleshooting approach and utilizing the free troubleshooting guide offered by Flight Systems, you can diagnose and repair many common issues. Remember to prioritize safety when working with generators and seek professional help if needed.

Backup Generator Option

If your Onan generator experiences prolonged downtime due to repairs, it may be beneficial to have a backup option available. One popular choice is the Champion 3100 RV-ready inverter generator. These portable generators can be purchased from various stores and provide a convenient power source while your primary generator is non-operational.

The Convenience of Onboard Generators

Onboard generators, like Onan generators, offer unparalleled convenience and reliability. With just the push of a button, you can have power whenever and wherever you need it. Whether you need to charge your batteries or run appliances in your RV, an onboard generator provides all the comforts of home on the road.

Pros and Cons


  • Immediate access to power with the push of a button
  • Convenient and easy to use
  • Reliable power source for RVs and other applications


  • Prone to specific issues that require troubleshooting and repair
  • Some repairs can be costly
  • Maintenance and occasional repairs may be necessary


Q: Can I fix a chewed-off wire in my Onan generator myself? A: If you have basic repair skills and are comfortable working with generators, you can attempt to fix a chewed-off wire. However, exercise caution, as there is a shock hazard when dealing with electricity. If you are unsure or uncomfortable, it is best to seek professional help.

Q: Where can I find the troubleshooting guide for Onan generators? A: The troubleshooting guide for Onan generators is available for free on the Flight Systems website. You can download the guide as a PDF file or print it out for easy reference during the troubleshooting process.

Q: Are Onan generators prone to start and stop issues? A: Yes, start and stop issues are a common problem with Onan generators. If your generator starts but immediately shuts off when you release the start button, it is likely experiencing this issue. Troubleshooting steps can help identify and resolve the problem.

Q: Is it necessary to unplug the 12-pin connector during troubleshooting? A: Unplugging the 12-pin connector allows for isolating the problem and testing different components with a multimeter. It is an essential step in the troubleshooting process to pinpoint the cause of the generator's malfunction.

Q: Can using a portable generator as a backup affect the performance of an Onan generator? A: No, using a portable generator as a backup should not have any adverse effects on the performance of an Onan generator. The portable generator serves as temporary power while the Onan generator is being repaired or serviced.

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