DIY Guide: Can You Replace a DC Alternator on a Diesel Engine Generator and Save Money?

When your diesel engine generator starts showing signs of trouble, one potential culprit could be the DC alternator. 

If you’re a hands-on individual with basic mechanical skills, you may wonder, “Can I replace a DC alternator on a diesel engine generator and save money?” 

The answer is yes, and this comprehensive guide will show you how to tackle this task effectively.

Replacing the DC alternator yourself not only saves you labor costs but also gives you valuable insight into maintaining your generator. 

Let’s explore the tools, steps, and tips you’ll need to confidently replace the alternator on a Perkins generator or similar models.

Signs Your DC Alternator Needs Replacement

Before diving into the replacement process, you need to determine whether your DC alternator is the problem. Here are some common signs:

1. Dim or flickering lights on the control panel.

2. Battery charging issues, such as a dead battery after prolonged use.

3. Unusual noises, like grinding or whining, near the alternator.

4. Burning smell caused by a failing alternator.

5. Voltage fluctuations during operation.

If your generator exhibits any of these symptoms, it’s time to inspect the DC alternator.

Tools and Materials Needed for Alternator Replacement

To replace the DC alternator on your Perkins diesel generator, gather these tools and materials:

1. Wrenches: Ensure you have the appropriate sizes for the bolts (10" bolts are typical for Perkins generators).

2. Socket set: For removing and tightening bolts.

3. Tensioning tool: To properly adjust the fan belt.

4. New DC alternator: Match it to your generator's model and specifications.

5. Replacement belts (optional): Check the condition of the fan belt during the process.

6. Multimeter: To test the electrical connections.

7. Gloves and safety goggles: For personal protection.

Step-by-Step Guide to Replacing the DC Alternator

Follow these steps carefully to replace your generator’s DC alternator:

1. Turn Off the Generator

• Ensure the generator is completely off and disconnected from any power source.

• Remove the battery connections to prevent accidental short circuits.

2. Locate the DC Alternator

• The DC alternator is usually mounted near the engine and connected to the fan belt.

3. Unbolt the Alternator

Perkins generators typically use three bolts for the alternator:

• One long bolt for the mounting bracket.

• Two shorter bolts for additional support.

• Use a socket wrench to remove these bolts, starting with the shorter ones.

4. Remove the Fan Belt

• Use a tensioning tool to loosen the fan belt.

• Slide the belt off the alternator pulley. Inspect the belt for wear and replace it if necessary.

5. Disconnect Electrical Connections

• Carefully disconnect the wiring harness and other connections from the alternator.

• Label the wires if necessary to ensure correct reinstallation.(wires going to the alternator, +, - and sometime neutral wire). 

6. Install the New Alternator

• Position the new alternator in place.

• Reattach the electrical connections, ensuring all wires are secure.
• Mount the alternator using the long and short bolts, tightening them securely.

7. Reinstall and Tension the Fan Belt

• Slide the fan belt back onto the DC alternator, crankshaft, and radiator fan pulley.

• Use the tensioning tool to adjust the belt to the proper tension. The belt should not be too tight or too loose; aim for about ½ inch of deflection.

8. Reconnect the Battery

• Reattach the battery cables(+ cable to battery + and, - cable to - battery terminal), ensuring the terminals are clean and tight.

9. Test the Alternator

• Start the generator and observe its operation.

• Use a multimeter to check the output voltage of the alternator. The voltage should be consistent with the generator’s specifications.

Tips for a Successful DIY Alternator Replacement

1. Refer to the manual: Consult your generator’s user manual for model-specific details.

2. Take photos: Before disassembling, take pictures to guide you during reassembly.

3. Double-check connections: Ensure all wires and bolts are properly secured.

4. Inspect related components: Check for worn pulleys, damaged belts, or corroded wires.

How Much Money Can You Save?

Professional labor for alternator replacement can cost anywhere from $150 to $500, depending on your location and generator model. 

By doing it yourself, you’ll only pay for the replacement part, which can range from $100 to $300, depending on the alternator’s brand and quality.

Is DIY Replacement Always the Best Option?

While replacing a DC alternator is straightforward, some situations may require professional assistance:

• If you lack the tools or confidence for the task.

• If the alternator failure has caused additional electrical issues.

In such cases, hiring a certified generator technician is recommended.

Conclusion

Replacing the DC alternator on a diesel engine generator, such as a Perkins model, is a manageable DIY project for those with basic mechanical knowledge. 

By following this guide, you can save money and ensure your generator continues running smoothly.

If you found this guide helpful, consider sharing it with others or leaving a comment below. 

For more tips on maintaining diesel engine generators, explore our blog at Sustainable Maintenance.