The voltage on my Onan 8 kw generator just dropped to 20 volts. Anyone have
any idea of the probable problem? It was running fine and suddenly stopped
working, breakers and fuses were all checked. its diesel powered. Would
appreciate any help from someone with knowledge.

On Sunday 24 October 2004 7:44 pm in rec.boats wreckless1 wrote:

The voltage on my Onan 8 kw generator just dropped to 20 volts. Anyone
have
any idea of the probable problem? It was running fine and suddenly
stopped
working, breakers and fuses were all checked. its diesel powered. Would
appreciate any help from someone with knowledge.

Check the brushes in the alternator.

--
My real address is crn (at) netunix (dot) com
WARNING all messages containing attachments or html will be silently
deleted. Send only plain text.

On Sun, 24 Oct 2004 14:44:30 -0400, "wreckless1"
wrote:

The voltage on my Onan 8 kw generator just dropped to 20 volts. Anyone have
any idea of the probable problem? It was running fine and suddenly stopped
working, breakers and fuses were all checked. its diesel powered. Would
appreciate any help from someone with knowledge.

I don't have an Onan, but a similar Kubota here at the house. The
following is based on my experience.

With constant revs on the engine, the chances are that it may be the
generator's control board which contains the rectifiers, etc. That's
a repair that can be done by a qualified mechanic.

Before you get nervous, however, check the brushes and make sure they
are still good.

Take care.

Tom

"The beatings will stop when morale improves."
E. Teach, 1717

egavasm relates:

-The voltage on my Onan 8 kw generator just dropped to 20 volts. Anyone have
any idea of the probable problem?-

Bilge-You might have a partial ground happening. Check voltage to ground on
each conductor, they should be equal,(this is assuming you do not have a
neutral line, as in residential/landside wiring.

This is called "chasing grounds" on the steel. If you have unequal voltages to
ground, start opening breakers, and checking that low leg to ground, until
(hopefully) you read equal voltages to ground. When you do, the fault is in the
last circuit(s) that you opened.

It's a lot easier, if practical, to start "upstream" and work "downstream" the
grid...feeder to distribution breakers, to individual component.

I had a ship once that ALWAYS showed a "breakfast ground" on the 220vac
circuit for the "house"...it was the toaster in the officer's mess. (yet
ANOTHER reason NOT to reach inside the slot with a knife or fork to try
salvaging yer bagel). Since I didn't have a spare toaster to hand, I just lived
with it.

WIth a "dead grid" you can also do this by measuring resistance to ground.

If you have external light fixtures, I'd look closely at those, condensation
does crappy things to 'em.

G'luck...be safe...guesswork in this trade is what kills people.




Mutiny is a Management Tool
Select Your Tattoo while Sober

"Among the many misdeeds of the British rule in India, history will
look upon the Act depriving a whole nation of arms, as the blackest."
-- Mahatma Gandhi

thanks for the input but the generator is an ac marine generator which is
brushless and uses a rectifier instead to produce the voltage.
"Chris Newport" wrote in message
news:3914557.aCFQic5eeO@callisto...
On Sunday 24 October 2004 7:44 pm in rec.boats wreckless1 wrote:

The voltage on my Onan 8 kw generator just dropped to 20 volts. Anyone
have
any idea of the probable problem? It was running fine and suddenly
stopped
working, breakers and fuses were all checked. its diesel powered. Would
appreciate any help from someone with knowledge.

Check the brushes in the alternator.

--
My real address is crn (at) netunix (dot) com
WARNING all messages containing attachments or html will be silently
deleted. Send only plain text.

"wreckless1" wrote in message
...
thanks for the input but the generator is an ac marine generator which is
brushless and uses a rectifier instead to produce the voltage.

I have never seen a brushless generator, and I would be really surprised to
find an 8KW genset built without them. My 6KW Onan marine genset certainly
had them. Are you sure you don't have brushes?

If you want specific help you should provide some specific details, like the
model number of the generator, or at least the year.

Rod McInnis

The generator I have is an 8kw 8-omdkd-3r-1b diesel serial # D850759014 it's
type is "a Revolving Field, 4-Pole, Brushless" I bought it used 3 years ago
and it has run fine the whole time. I have a parts catalog which shows the
generator assembley and while there is a rotor, stator and excitor, and
rectifier I do not show any brushes per se.


"wreckless1" wrote in message
...
The voltage on my Onan 8 kw generator just dropped to 20 volts. Anyone
have
any idea of the probable problem? It was running fine and suddenly
stopped
working, breakers and fuses were all checked. its diesel powered. Would
appreciate any help from someone with knowledge.

On Mon, 25 Oct 2004 15:05:41 GMT, Short Wave Sportfishing
wrote:

Only one rectifier on a 8 KW generator?

===================================

Integrated full wave bridge assembly?

On Mon, 25 Oct 2004 12:36:19 -0400, Wayne.B
wrote:

On Mon, 25 Oct 2004 15:05:41 GMT, Short Wave Sportfishing
wrote:

Only one rectifier on a 8 KW generator?

===================================

Integrated full wave bridge assembly?

Would almost have to be - a potted module probably which makes trouble
shooting impossible.

Later,

Tom

"Beware the one legged man in a butt
kicking contest - he is there for a
reason."

Wun Hung Lo - date unknown

On Mon, 25 Oct 2004 17:19:39 GMT, "Chad Hansen"
wrote:


"Short Wave Sportfishing" wrote in message
.. .
: On Mon, 25 Oct 2004 08:36:05 -0400, "wreckless1"
: wrote:
:
: The generator I have is an 8kw 8-omdkd-3r-1b diesel serial # D850759014
it's
: type is "a Revolving Field, 4-Pole, Brushless" I bought it used 3 years
ago
: and it has run fine the whole time. I have a parts catalog which shows
the
: generator assembley and while there is a rotor, stator and excitor, and
: rectifier I do not show any brushes per se.
:
: Only one rectifier on a 8 KW generator?
:
: Interesting.
:
: I'm still suspecting the rectifier circuit.

Bases on the symptom of low voltage output(20vac)if u could give me a ohm
reading across the stator as well as the field I can help.

Something just occurred to me. I wonder if the field is collapsing on
him. Twenty volts is almost like a left over residual charge - it
may not be the rectifier at all.

Hmmmm........

Take care.

Tom

"The beatings will stop when morale improves."
E. Teach, 1717