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Onan generator field breaker replacement
Posted: September 22nd, 2025, 12:18 pm
by KyleR
Hey everyone. My circa 2002 Onan generator (10KW Model MDKWB) has a bad field breaker. Unfortunately there are no real identifying specs on the breaker itself other than the manufacturer, Airpax, and a bunch of patent numbers. (See pics attached)
I did find a part number in the parts manual: 320-1769. Unfortunately trying to search that hasn't yielded much either.
If I could get the specs/ratings I can get a like-for-like part, which is probably my best hope. I'm just not sure what ratings to look for.
I reached out to Airpax but no reply yet.
Thanks in advance!
Kyle
Re: Onan generator field breaker replacement
Posted: September 22nd, 2025, 1:21 pm
by KyleR
Followup: I called Onan on a whim and that part number is actually still active and a available, for nearly $75! Typical though of my experience with other Onan parts.
However, I did find out it is a 5amp breaker so I am thinking about using this:
https://a.co/d/f6IWxuaAny electrical gurus out there have any insights on if this would possibly be an acceptable replacement? Thanks again!
Re: Onan generator field breaker replacement
Posted: September 22nd, 2025, 1:42 pm
by km1125
I'm surprised there are no other markings on the old breaker!! I don't think I've ever seen one that doesn't have at least the basic ratings for the device, much less an actual part number.
Where did you come up with the 5A number? If that is the rating of the old breaker, or the field never exceeds 5A, then I'd bet that new breaker in the link you posted would be fine.
Re: Onan generator field breaker replacement
Posted: September 22nd, 2025, 2:04 pm
by KyleR
I'm surprised there are no other markings on the old breaker
Me too! I thought this was going to be pretty simple - but nothing is!

Where did you come up with the 5A number?
It was listed in the description on the Onan parts website. No other specs though (e.g. voltage, time delays, etc).
Thanks for the feedback!