Fixing Portable Generators – No Output Power

Why Your Generator Runs But Produces No Power – The Role of Residual Magnetism

If your portable generator runs but doesn’t produce power, you’re not alone. This is one of the most common generator troubleshooting issues reported by homeowners, contractors, and RV owners. Understanding why a generator runs but has no voltage output is essential for restoring power quickly, especially when backup power is critical.

One of the primary culprits? Loss of residual magnetism.

What Is Residual Magnetism and Why Does It Matter?

All generators rely on magnetism to create electricity. When your generator starts, a small amount of magnetism—known as residual magnetism—is used to generate an initial low voltage, which then feeds into the excitation system to produce full power. Without this leftover magnetism from a previous run, the generator has no way to “kick-start” the process of power generation.

“If residual magnetism is lost, your generator will produce no power at startup.” — Why Does My Generator Run, but Not Produce Electricity?

Common Causes: Why Residual Magnetism Is Lost

If you’re wondering why your generator is running but not generating electricity, here are some common causes of residual magnetism loss:

• Prolonged storage or inactivity
• Shutting down with a load connected
• Running the generator without a load for too long
• Transport vibration (common with new generators)
• Fuel starvation under load (e.g., generator runs out of fuel mid-use)

“Loss of residual magnetism may be caused by having a connected load when the generator is shut off, or by running your generator for too long with no load.” — Fixing Portable Generators with No Power

Other Common Reasons a Generator Produces No Power

While residual magnetism is the most common issue, it’s not the only reason a generator has no voltage output:

• ✅ Tripped breaker or GFCI Always verify that all breakers are reset and functioning properly.
• ✅ Faulty AVR (Automatic Voltage Regulator) A failed AVR can prevent voltage build-up.
• ✅ Damaged capacitors Some generators use a capacitor instead of an AVR to build voltage.
• ✅ Worn carbon brushes or slip rings These are essential for transferring power from the rotor to the stator.
• ✅ Excitation winding issues Broken or grounded windings prevent the generator from energizing.

How to Restore Power: Flashing a Generator

When residual magnetism is gone, it can often be restored using a process called flashing the generator. Here are two proven methods:

1. The 12V Battery Method

• Disconnect the AVR or excitation wire (consult your generator manual).
• Briefly apply 12V DC from a car battery to the field windings.
• This jumpstarts the magnetic field needed for power production.

“The 12-Volt Generator Battery Method involves applying battery voltage to the excitation circuit to rebuild magnetism.” — Fixing Portable Generators – No Power

2. The Electric Drill Trick

• Plug a corded drill into the generator.
• Start the generator with the drill’s trigger pressed.
• Spin the drill chuck backwards by hand. This sends a small current back into the generator.

“The corded drill trick works as a way to field-flash a generator and restore power output.”

Preventing Future Power Loss

To ensure your generator always produces power, follow these best practices:

• ✅ Run the generator under load regularly
• ✅ Disconnect a