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Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 14889
Experience:  Certified on Onan and Generac generators
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Have an Onan 4.0. Has sat so carb was replaced by original

Customer Question

Hello, Have an Onan 4.0 KY. Has sat for awhile so carb was replaced by original owner . Unit output voltage 113vac-114vac out of coach no load, freq 53-55hz. Cannot get more then 56hz by adjusting engine speed screw before it shuts down with code 14, Ive been working on Onans for sometime and have never seen this issue in a 4.0. Any ideas
Submitted: 1 year ago.
Category: Small Engine
Customer: replied 1 year ago.
update, voltage is now at 120vac, freq 54-55. any higher and set shuts down and throws code 14 over freq. Two different meters used so eliminate meter as problem
Expert:  Hank F. replied 1 year ago.

Hello, thanks for requesting me.

If you were getting 114VAC @ 53-55 Hz, but are now getting 120VAC at 54-55Hz, there is a problem. If you adjusted the engine speed that much, the frequency should have really spiked.

There are 2 possibilities here.

1. You are using a digital meter. It is not very common with Onan, but sometimes you just have to resort to using an old analog meter. An analog meter does not show spikes. Even using a True RMS meter sometimes is not acceptable.

2. You may have a brush sticking in the holder. Although this most often would result in a higher frequency reading than what it is actually running, it is possible that you could get a lower reading. I have never seen this happen, though.

If the genset is actually shutting down before it gets up to 60 Hz, it is possible that the controller is bad. I have never heard of this happening, though.