Genny quits under a heavy load

[danf7]

I have a Onan 6000 W quiet diesel. SHe starts up with no issues and runs fine with small loads. If I put on either AC she shuts down. I thought the problem was low coolant so I change that. She was good at home. Ran both AC's for over an hour. I start a 7 week road trip and it dies leaving the driveway. We only use it for traveling between campgrounds, but we use it each time. Last year ran perfect all the way to DC and back to Ma. First couple of camp outings this year was no issue until the last short one it died. That's when I noticed that the coolant was low, so I changed it ans seemed to be ok. Then it acted up again. It is a 2008 and has 78 hours on it. I know that is low , but it does run every month during the summer. Any thoughts would be appreciated.

Dan

[Route 66]

Is the pilot light on the start switch flashing an error code when it shuts down?

[danf7]

Yes I get a code 11 which is a load issue. (ac output short ) Ir runs fine on a small load, it just can't handle the ac's.

[Route 66]

If there was an actual overload, a circuit breaker would trip, plus you stated it did work OK in the past.

I suspect a fault with the internal inverter, which falsely senses an overload.

It sounds like a trip to an Onan service center is needed.

[RJay]

Hi Dan,
I'm assuming you have a gas generator. I sounds to me that you have a problem with your voltage regulator. The regulator maintains voltage at a constant 120 VAC. As a load is added to the generator the regulator increases the DC field voltage to the generator causing a corresponding increase of the AC voltage to compensate. If the load is increased without a corresponding AC voltage increase the generator will shut down because it can't maintain the required AC output voltage.


As load is added to the generator there also should be a noticeable increase in RPM. If your not hearing this increase in RPM the required frequency will not be maintained and will shut down. In this case it's likely you have a gummed up carburetor or an out of adjustment governor.

[danf7]

It is a diesel generator.

[bthomforde]

A cheap and easy thing to try is replace the fuel filter.

[rgreen45]

Quote:

Originally Posted by RJay [FONT=Verdana, sans-serif][SIZE=2] As load is added to the generator there also should be a noticeable increase in RPM.

I believe this statement is not correct. Generators are built to run at 1800 rpm. As the load increases, the engine load also increases and the governor sends the needed fuel to maintain the 1800 rpm. There is however, an obvious difference in the sound of the engine. Think of it as climbing a hill while in cruise control. Same rpm but different load and sound.

edit to add: If you don't maintain the 1800 rpm, the Hz won't be within specs.

[danf7]

At least with my diesel you are correct. (This is my third Rv ,but first with a genny) The rmp's are not all that different once she has the juice flowing up to speed.