Re: HELP! Onan Emerald III No AC
- From: "Alan Robinson" <alr@xxxxxxx>
- Date: Sun, 17 Jun 2007 19:27:42 -0700
"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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