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Ask Hank F. Your Own Question
Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 14808
Experience:  Certified on Onan and Generac generators
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I have a 3.7 kw generator 240V it is only producing 80V, I

Customer Question

I have a 3.7 kw generator 240V it is only producing 80V, I have tested the AVR and it is good, I have checked the stator windings they too are good. I'm getting 2.8 V on each winding when the unit runs with the AVR disconnected. any ideas?
JA: What's the make and model of the generator? And can you guesstimate how old it is?
Customer: its a Yanmar YDG3700N its about a 2008?
JA: Do you plan on doing the work yourself?
Customer: Yes
JA: Anything else we should know to help you best?
Customer: not that I can think of. I have two of the same unit so I have been testing it against the other one
Submitted: 5 months ago.
Category: Small Engine
Expert:  Hank F. replied 5 months ago.

Hello, my name is ***** ***** I am going to assist you with this.

Connect a frequency meter to the unit, and check the frequency with no load on the genset.

What is the frequency of the output?

Customer: replied 5 months ago.
50Hz
Expert:  Hank F. replied 5 months ago.

If the genset is running at the proper proper frequency, but has low voltage, it means that the voltage regulator is bad.

Customer: replied 5 months ago.
That's what I thought? I have swapped the AVR from the working unit and the problem is there?
Expert:  Hank F. replied 5 months ago.

And the other unit works correctly?

Customer: replied 5 months ago.
Year the other unit runs fine. I have been using it to test the parts on the non running unit
Expert:  Hank F. replied 5 months ago.

There are only a few things that will cause low voltage - bad AVR, dirty/worn slip rings/brushes, low engine speed, or a damaged stator.

We have verified the engine speed is correct, you said the stator tests good, and hace tried a different AVR.

Check the brushes and clean the slip rings.

Expert:  Hank F. replied 5 months ago.

Did you find anything?