Community Forums

Papa_Jim · 07-09-2010, 08:42 PM

Our Onan 6500 propane generator has been a good performer, but just recently it has begun to 'surge' under light to no load. It starts O.K., works fine under load. With light to no load it surges, it can't maintain a steady R.P.M. The volt gauge rises and falls appropriately. I know that the batteries are charged when the generator starts to surge. It'll get doing it badly enough that I turn it off.

Coincidentally??? I changed spark plugs, oil and filters a few months ago. It just started this behavior in the last few days.

Anybody experience this before?

F&D ABQ · 07-10-2010, 08:58 AM

Surging is usually a consequence of too-little use. Have you been exercising it under load for an hour each month?

Gary RVRoamer · 07-10-2010, 10:23 AM

Odd that it runs fine under load but no when idling. Most of the usual causes for surging would affect the loaded state too. I'd have to suspect the voltage regulation function, which controls the speed.

Papa_Jim · 07-10-2010, 10:15 PM

Thanks for the replies. Under use is not a problem in this case. As we travel, we usually park where there are no services. The generator gets to run for at least an hour in the evening to charge the batteries as we watch TV and work on our computers. My wife and I both use CPAP machines, so by morning, the batteries need charging. I usually let the generator run for 1/2 hour to 1 hour while we're getting ready to roll.

I ran both air conditioners today for three hours. Each air conditioner is a 13500 unit, and the generator worked perfectly. I turned off the air conditioners, and within 5 minutes, the generator was surging. I looked at the panel, and saw that the batteries were fully charged, so the generator had no load.

I turned one air conditioner back on, and the generator got down to business and smoothly provided the power needed to run the air conditioner. I turned the air conditioner off, and within a couple of minutes, the generator was surging. I turned it off.

So, under load it's O.K. With no load it's not. Although, when I first start it, if it has no load it runs smooth. It seems to happen after it has worked hard for a while, then when the load becomes light, it goes into surge mode.

F&D ABQ · 07-11-2010, 08:14 AM

If it were I, I'd pat myself on the back for having isolated the problem and go to my nearest authorized Onan service center. But there may be a tech out there who can tell you how to adjust the linkage yourself.