Generator Runs But Produces No Power
In This Guide
A generator runs but no power reaches anything you plug in, and it is unsettling precisely because the engine sounds perfectly healthy. It starts, it runs, it purrs away, and yet nothing you plug in comes to life. The reassuring news is that the engine genuinely is fine. The fault is in the electrical side of the generator, the alternator, and the most common cause is one that sounds far worse than it is.
First, the Two Second Checks
Before assuming anything internal, rule out the two simplest causes, because they are also common.
1. Reset the breaker
Generators have circuit breakers, and a tripped breaker cuts all output while the engine runs on happily. Switch it fully off, then on.
2. Check any GFCI outlets
If the generator has GFCI protected outlets, a tripped GFCI stops power at those sockets. Press the reset button.
If resetting these restores power, you are done. If not, read on, because the cause is almost certainly loss of residual magnetism.
The Main Cause: Loss of Residual Magnetism
This is the big one, and it is worth understanding because it explains so many no power faults.
A generator makes electricity using magnetism. It relies on a small amount of leftover magnetism, called residual magnetism, held in the iron core of the rotor after the generator is switched off. That tiny bit of leftover magnetism is the seed that lets the generator build up its full magnetic field and start producing power the next time it runs.
Over time, that residual magnetism can fade away, and when it does, the generator spins perfectly but the magnetic field never builds, so no electricity comes out.
The Fix: Flashing the Field
Restoring lost residual magnetism is done through a process called flashing the field, which reintroduces a small amount of magnetism to the rotor using an external DC source such as a battery or a drill.
In principle the process reconnects magnetism to the rotor for a few seconds, after which the generator builds its field normally again. In practice, the safety caveats are why it is a common reason people call us.
If Flashing Doesn't Fix It: The AVR
The Automatic Voltage Regulator, or AVR, controls and stabilises the generator's voltage output. When it fails, the generator can produce no power at all, or wildly unstable power.
An AVR is a replaceable part rather than a catastrophe, and it is a common failure. If the field has been flashed and the generator still produces nothing, a failed AVR is the leading suspect. It must be matched to the generator model.
Other Electrical Causes
| Cause | What happens |
|---|---|
| Worn carbon brushes | On brushed generators, worn brushes break the transfer of current. Replaceable. |
| Blown capacitor | On brushless generators, a bad capacitor stops voltage building. Replaceable. |
| Loose or broken connection | A wire in the excitation circuit come loose. Sometimes a simple fix. |
| Low engine speed | If the engine runs too slowly, an under frequency circuit can cut output. |
Why Prevention Beats Repair Here
Almost everything on this page is prevented by the same two habits. Because loss of residual magnetism is the leading cause, and because it is caused by improper shutdown and long idleness, you can avoid the whole problem.
Rather Have a Real Technician Handle It?
A Wildwood technician comes to your home, diagnoses the generator on site, and gets it running, usually in about an hour. More than 10,000 repairs completed since 2019, with flat rates quoted before we arrive so there are no surprises. When you need power back, you need it back now.