Onan 7500 diesel gen set

Thanks everyone for the inputs. I plan to do a full service this weekend. From hour comments, it sounds like I'm just reading (hearing) too much into it. Will feel much better after I complete the service and start fresh.

Thanks everyone

My 7500 QD will surge for a while...then stops once all the loads are stabilized. Once it is just operating the A/C's the rpm's are steady.

One other point, mine does not like to operate with little to no load, will surge significantly if both A/C's are not running.

Your problem, if any is minor IMHO.

bluwtr49 wrote:
The 7500 QD gen set is controlled by an inverter and the speed changes as the load changes. Suggest you make sure this "Surging" is not just normal operation.

This was my first thought. Higher load equals higher engine RPM with this model. If things like water heater elements or air conditioners (high loads) are switching on and off it's normal to have a significant change in RPM.

The 7500 QD gen set is controlled by an inverter and the speed changes as the load changes. Suggest you make sure this "Surging" is not just normal operation.

What trouble code did it give you? Look in the generator manual and it will tell you how to get the code. This will tell you what you need to do.

I'd start with a full service. It's an inverter genset so RPM s vary with load.

It might be adjusting to a varying load. It shuts off if it can't regulate voltage and frequency and gives you a trouble code.