My gennie stopped putting out power this weekend.

We had a power outage for couple hours so I ran the gennie. Started out like normal, ran the house fine, but after a while even though the engine was running smoothly there was no power out of the outlets. I read about the process of flashing the generator where you plug in an electric tool and manually run it backwards. I understand how electricity works and how motors work and how windings work.

What does flashing do from an engineering perspective?

Also the capacitor had a big brown mark. New one is on order. Likely the issue.

It's a Winco dual fuel 6K. Pretty great. Runs the whole house just fine.

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    More often written 'genny' or 'gennie'. Jul 12, 2021 at 18:37
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    Well, it'd certainly help if you'd edit your post to replace the word "genie" with whatever is the actual correct word for whatever you mean. Your question lacks other important details, like a link to whatever references you found that referred to "flash", and an explanation about why a simple web search didn't prove useful to you (there are lots of results for "flash a generator"), as well as includes irrelevant details that only detract from the question. Jul 12, 2021 at 19:03
  • More info would be useful. De-excitation from disuse seems unlikely given the generator failed during use. Not sure what role a capacitor plays as my generator does not have one, but likely related to charging the battery and providing DC power to onboard electronics. Perhaps the battery charging has failed, subsequently the battery is drained, and some component requiring DC power is dead. Does the electric starter crank on battery? Otherwise you may have a more serious problem. See lots of diagnostics tutorials here: youtube.com/channel/UCr_GXW2Y56hOpGchXYNqZOQ
    – jay613
    Jul 14, 2021 at 19:09

2 Answers 2


Sounds like you're talking about a self-excited generator.

Modern generators with field coils are usually self-excited; i.e., some of the power output from the rotor is used to power the field coils. The rotor iron retains a degree of residual magnetism when the generator is turned off.



Ok, I'll bite.

Residual magnetism in the generator exciter field allows the generator to build up voltage during start-up. This magnetism is sometimes lost due to shelf time or improper operation, among other reasons. Restoring this residual magnetism is possible and is sometimes referred to as "flashing the exciter field".


Home generators in storage can “go flat” or lose their magnetism. Then they will not produce electricity, even though the small gasoline engine turning them is running just fine. There is a simple way to fix that, however. ... It takes electricity of the correct voltage and frequency to reestablish the magnetism in the generator to produce electricity.


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    so you're saying that the magnet can become an iron bar and doing this makes it a magnet again?
    – Trout
    Jul 12, 2021 at 22:49
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    @Trout -- exactly, the iron core in the rotor can lose its magnetism, and "flashing" makes it a (weak) magnet again Jul 14, 2021 at 20:00

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