Re: HELP! Onan Emerald III No AC

Thanks for the advice Alan. What you said makes alot of sense. I didn't get
to do a lot tonight as I am having a different issue now. It started up the
first time and of course it blew the DC fuse nut it did start for a couple
of seconds. I replaced the fuse and let it sit for a minute. I tried
starting it up again and it would barely turn as in: the starter turns very
slowly and the engine turns with it but not near fast enough for it to
start. I let it sit for another half hour or so and it does the same thing.
I'm no expert but I am guessing it is either flooded or the battery is low
(I'm throwing the charger on it now). Anything else I should look for given
the symptoms? Otherwise I will try it again tomorrow. Thanks again for all
of your help.

You are correct, when it does run but gives no AC I am able to let go of the
start switch and it keeps running.

Quentin

"Alan Robinson" <alr@xxxxxxx> wrote in message
news:5dm8srF34okcdU1@xxxxxxxxxxxxxxxxxxxxx

"QBall" <qNOacyoung@xxxxxxxxx> wrote in message
news:qBkdi.523146$6P2.91077@xxxxxxxxxxxxxxx
An update on the issues:

I have tried several times today to start the gen set back up. When it
does kick in and supply 120VAC it blows the DC (5A slo-blo) fuse quickly
after starting and the motor shuts off. If it does not produce 120VAC the
motor purrs along just fine and does not blow the fuse. Seems very random
whether it wants to produce the proper voltage or not. I haven't been
able to find an issue like this in any of my searches. Thanks again.

Quentin
"QBall" <qNOacyoung@xxxxxxxxx> wrote in message
news:Duddi.467857$115.89876@xxxxxxxxxxxxxxx
Hello all,

I purchased a used motor home about a week ago. It is equiped with an
Onan Emerald III 6.5KW gen set. The model and serial are as follows:

Model: 6.5NHE-1R/26100A
Serial: 1850777605

Here is the story of how I got to the point I am at (sorry for the
wordiness but I wanted to be as detailed as possible).
The generator had been working great all week. A few days ago (shortly
after I changed the oil and filter) the unit began to surge/hunt when
under heavier loads to a large degree. I did some reading of various
articles on the net and decided to make some adjustments to the governor
etc (not my brightest idea). I applied the load and the surging was
greatly reduced. I ran the gen set for awhile and decided to turn
everything off and shut it down. When I shut off the load the gen
sounded as though it was running at a higher than normal speed. Before I
could turn it off it shut itself down. I tried to restart but did not
get any response. I found that the dc fuse was blown. I purchased a
replacement and installed it. The generator started right up and sounded
normal. I checked AC on the fluke and it showed 7-8 VAC. It was already
late so I gave up for the evening.
I came out the next day with tools in hand to investigate. Started the
gen up, checked the output and all was normal, 120V. Started one of the
air conditioners and everything was fine. I let it run for awhile and
started the second air conditioner. It surged very briefly and kept
running. After about 20 mins of running the second AC it began to surge
and died. I shut down everything, waited a bit and tried to restart
again. No response, as before. The DC fuse was blown again. Replaced the
fuse and now I am back to the 7-8 VAC output. The motor runs perfect
just no output.

Where should I go from here? I have read articles regarding several
checks on the votage regulator for no AC issues. Is this where I should
start? Thanks in advance for your assistance. And yes I learned my
lesson "If it ain't broke, don't fix it"

Quentin




Ok,
It's hard to give you something definite - but it sounds like you may
have two issues here. Unless something is really messed up, there just
isn't that much to go wrong on your set - it's what is known as a
'transformer regulated' set - no electronic voltage regulator. You didn't
explicitly say, but I presume that when the motor just purrs along,
doesn't produce 120vac, and doesn't blow the fuse, that it's doing this
with your finger off the start switch? If so, it appears that your
set -is- generating, you're just not seeing the output wherever you are
checking - it HAS to have approx 36vac on the battery charge windings to
energize K2 relay, which is one of two relays that have to actuate to
switch from 'start' mode to 'run' mode. Try this - remove the black
plastic cover from the electric choke mechanism - you'll see two terminals
with wires attached. Check the ac voltage at this point - should be approx
36vac. If you see the voltage here, then it's generating - you're just not
seeing the ac output from the output windings. I suspect that when you
do - briefly - have 120v output from the main windings you'll find that
this voltage is considerably higher, and (after it's rectified by CR1 on
the control board) is trying to charge your battery with a voltage high
enough that it blows the fuse from excess current.

The 'transformer regulated' sets - such as yours - do not have 'absolute'
voltage regulation. As current through the transformer increases, it will
increase the current fed to the field - if the right taps have been
selected, this increase will be what's needed to maintain the output
voltage close to what it was with no load. But the voltage it starts with
at no load is a function of two things - the tap(s) selected on the
transformer, AND THE SPEED THE GENSET IS RUNNING. If the genset is running
too fast, the voltage from the output winding AND the voltage from the
battery charge winding will be high. I've seen some sets come in putting
out over 160v! The FIRST thing you need to do - since you say you did play
with the governor - is make sure that the genset is running at the correct
speed. With no load, it should be at approximately 1890 rpm, which would
give 63hz output - and make SURE that at no load, the idle stop on the
carburetor isn't touching - pressing the linkage back against the idle
stop should slow the set down to approx 1650 rpm - which would be 55 hz
output. Get to that point, and I'm pretty sure it will stop blowing the 5A
fuse - then it will be safe to investigate why it sometimes isn't giving
ac output.

Oh, by the way - surging under load is usually a fuel supply issue, not a
governor issue. If the governor is too sensitive, it'll usually show up at
no load or on load changes, not with a reasonable load.

Alan




.

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