Generator voltage drop

[ezgoin]

Fired up the genny today to "exercise" it as recommended. After a few minutes the voltage started dropping to about 110 volts every 2 seconds or so then back up to 120 volts. It kept cycling like this for a couple of minutes before I shut it off. I have no electrical skill so I guess I'll need to know what to tell tech to look for???? Ideas?

Thanks, Bill

[SCVJeff]

Yeah, with the air conditioner or large heater

[ezgoin]

2112 wrote:

ezgoin wrote:
I tried suggestion of plugging in a space heater and let it run today. The longer it ran the less the voltage drop until it smoothed out and returned to normal sounding operation with no straining.

How long did it take to smooth out? My champ smooth's out in about 30 seconds.

It probably took 3-4 minutes. The longer it ran the drops were less frequent and and shorter in duration. At least now I have a better idea of how to exercise the genny.

[profdant139]

The same thing happened with my Honda 2000 -- the guy at the fix-it shop showed me how to drain the carb after every use prior to storage of more than a couple weeks. So now I do that, and run it every month under a 1500 watt load (a heat gun) for a half hour, and add a little Seafoam to the tank every time. Problem solved, so far.

The whole point is to keep gunk out of the carb jets. The bad gas in Calif. makes this essential. If you can find non-ethanol gas, you will have fewer carb problems than I do.

[gatorcq]

Start using Sea-Foam in the (assuming it is GAS) in the main tank.
Sounds more like the jets are a little clogged.

Or just run it longer, as if it is a jet, it may eventually clear up.
Longer being 1 to 4 hours

[2112]

ezgoin wrote:
I tried suggestion of plugging in a space heater and let it run today. The longer it ran the less the voltage drop until it smoothed out and returned to normal sounding operation with no straining.

I can't speak for high-end RV units but this is common with smaller open frame models. Now you know to apply a load while exercising your genny. I have two 500W flood lights just for this purpose.

How long did it take to smooth out? My champ smooth's out in about 30 seconds.

[ezgoin]

I only ran it with no load for a few minutes for it warm up when it started dropping voltage and straining as if under load, but there was no load except one digital alarm clock. I tried suggestion of plugging in a space heater and let it run today. The longer it ran the less the voltage drop until it smoothed out and returned to normal sounding operation with no straining. So thanks all for the suggestions and help. This is why I love this forum. You all are a great bunch. Thanks.

[SCVJeff]

You ARE exercising it under load aren't you? Running a generator under zero load is a good way to start a next summer project to de-carbonize it. Either way it sure sounds like something is cycling

[TEXAS]

Need more information than that. But if it is one of the belt driven units.Gensection sitting vertical. I would look closely at the top bearing of the generator. They have been known to wear out the end bell. Letting the rotor wobble in the housing.

[ezgoin]

TEXAS wrote:
Would help to know what generator. You are talking about. But small voltage changes are normal as load changes.

Generator is Onan 5500 and it had no load on it. It was only idling.

[TEXAS]

Would help to know what generator. You are talking about. But small voltage changes are normal as load changes.

[PaulJ2]

Sounds like my portable generator when i forget to open the air vent on the gas cap.

[2112]

Put a resistive load such as an electric heater on it and see if it clears up after a minute or so. My Champion does the same thing if I haven't ran it for a few months. It smooths out once it sees a load.

[ksg5000]

Not sure what type generator your operating but in the std Onan generator the voltage/frequency is a direct correlation to the revolutions/speed of the generator. If your generator is sputtering because of carb issues or spark plugs your going to see a corresponding impact on voltage. If your operating with "no load" then maybe a simple tune up will resolve the problem - even running it for a few hours with a load (electric heater) may help resolve the problem.

[DrewE]

It also sounds to me like it probably is a load that's cycling on and off. Maybe you have thermostatically controlled heaters somewhere (tank heaters? heat strips for the AC?) that usually don't operate because you're in Sunny Arizona. Do you happen to have an AC ammeter to watch the current draw? That would show pretty quickly if that's the cause.

One other possibility that comes to mind is a bit of air in the fuel line for the generator, either because the fuel tank level is right near the end of the pickup for the generator (typically around 1/4 tank), or because there's a little air in the fuel line to the generator that needs to work its way out. In the former case, the generator would stall after running for a bit more; in the latter case, the rough running would clear up.

As Gordon says, 110V is not an unreasonable output voltage under a decent load, particularly if the governor hasn't had time to stabilize from the added load.