Onan troubles

R

richard waters

New member
Feb 8, 1999
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I've had a good time during this first full season
with my GMC. I've managed to drive it over
10,000 miles since April. about 6,000 since leaving
for Forest City. I'm going to keep driving it
until the first week in January because it will be
my APU for the house in case the dreaded Y2K
kills our power at the house for a while.

For the most part it has been as trouble free as you
could expect a 24 year old vehicle with 130,000 miles.

I do have a problem with my Onan. It does not
consistently hold a constant voltage. Sometimes it
runs just fine for hours and hours. Then all of a
sudden it will decide to cycle between 90 volts and
140 volts. It will do that for a while and then I'll
worry that will wreck something, so I'll shut it down.
The next time I run the Onan it will run just fine for
a few hours.

One time I was running the microwave and when it
finished my TV dinner, the voltage surged past 140
volts. The microwave stopped heating after that. I
guess the surge fried the microwave. Oh well I did
want a new combination microwave convection
oven.

I've replaced the points, plugs and lubed all the
movable parts that I can see on the top side. They
all seem to move as they should.

Any ideas as to what I can do would be appreciated

Richard Waters '76 PB, Troy

PS...The other day I found a great way to need a new
muffler or wake up your spouse:-) Just drive along at
about 25 MPH in your GMC and turn off the ignition
for a few seconds and turn it back on. The sound that
makes is very stimulating to say the least!

I did that because I wanted to see how well the brakes
and steering work with the engine off. I neglected to
put the trans in neutral before my test.

The resulting explosion blew the rear end of the driver's
side muffler right off! I had to drive 250 miles from
just South of the Mackinaw Bridge to home like that.
I bet John Wright could hear me as I passed by near his
house. It was VERY, VERY LOUD!

Fortunately, all I needed was a new muffler. Everything
else seems OK.

I probably should not have made this confession here
on the internet with guys like Mike Beaton just waiting to
make fun of a U.S. citizen. Oh well!
 
Richard,
I thought that I heard something familiar coming thru the trees from the x-way.
I know the sound, I damage a muffler about a year ago when the
alternator quit and the voltage fell off to the engine when the battery
was going low. It can be quite impressive as you rumble down I-75.

J.R. Wright
GMC GreatLaker
77 Eleganza II
Michigan

>
> I've had a good time during this first full season
> with my GMC. I've managed to drive it over
> 10,000 miles since April. about 6,000 since leaving
> for Forest City. I'm going to keep driving it
> until the first week in January because it will be
> my APU for the house in case the dreaded Y2K
> kills our power at the house for a while.
>
> For the most part it has been as trouble free as you
> could expect a 24 year old vehicle with 130,000 miles.
>
> I do have a problem with my Onan. It does not
> consistently hold a constant voltage. Sometimes it
> runs just fine for hours and hours. Then all of a
> sudden it will decide to cycle between 90 volts and
> 140 volts. It will do that for a while and then I'll
> worry that will wreck something, so I'll shut it down.
> The next time I run the Onan it will run just fine for
> a few hours.
>
> One time I was running the microwave and when it
> finished my TV dinner, the voltage surged past 140
> volts. The microwave stopped heating after that. I
> guess the surge fried the microwave. Oh well I did
> want a new combination microwave convection
> oven.
>
> I've replaced the points, plugs and lubed all the
> movable parts that I can see on the top side. They
> all seem to move as they should.
>
> Any ideas as to what I can do would be appreciated
>
> Richard Waters '76 PB, Troy
>
> PS...The other day I found a great way to need a new
> muffler or wake up your spouse:-) Just drive along at
> about 25 MPH in your GMC and turn off the ignition
> for a few seconds and turn it back on. The sound that
> makes is very stimulating to say the least!
>
> I did that because I wanted to see how well the brakes
> and steering work with the engine off. I neglected to
> put the trans in neutral before my test.
>
> The resulting explosion blew the rear end of the driver's
> side muffler right off! I had to drive 250 miles from
> just South of the Mackinaw Bridge to home like that.
> I bet John Wright could hear me as I passed by near his
> house. It was VERY, VERY LOUD!
>
> Fortunately, all I needed was a new muffler. Everything
> else seems OK.
>
> I probably should not have made this confession here
> on the internet with guys like Mike Beaton just waiting to
> make fun of a U.S. citizen. Oh well!
 
yah but how did the brakes work????

gene

>
>> PS...The other day I found a great way to need a new
>> muffler or wake up your spouse:-) Just drive along at
>> about 25 MPH in your GMC and turn off the ignition
>> for a few seconds and turn it back on. The sound that
>> makes is very stimulating to say the least!
>>
>> I did that because I wanted to see how well the brakes
>> and steering work with the engine off. I neglected to
>> put the trans in neutral before my test.
>>
>> The resulting explosion blew the rear end of the driver's
>> side muffler right off! I had to drive 250 miles from
>> just South of the Mackinaw Bridge to home like that.
>> I bet John Wright could hear me as I passed by near his
>> house. It was VERY, VERY LOUD!
>
>Richard,
> ROTFLMAO!!! When I was a young lad back in the Sixties, this was common
>practice for many if not most mildly delinquent teen males! (We didn't have
>$3,000 / 3,000 watt stereo systems to annoy the townspeople, like they do
>today.) We'd select a suitable down grade, and shut the ignition off. The
>carburetor and mechanical fuel pump would continue to function (as you
>discovered!), filling the exhaust system with a nice flammable mixture,
which
>would produce a satisfying when the key was turned back on. You
>could often produce a 6 foot long flame from the tailpipe to accompany the
>sound effects.
> When I was about 13, I remember my cousin (who was 3 years older than I)
>borrowed my stepmother's '57 Ford, and, of course, couldn't resist trying
>this gambit. Trouble was, as he coasted silently and key off down the long
>hill into downtown Melrose, Massachusetts, he spotted a policeman standing
on
>the sidewalk just as he was about to light it off. Not daring to make a big
>bang right in front of the officer, poor Lennie had to coast on for another
>block and a half. When he finally turned it back on, the result was just
>like yours: the muffler split wide open from knave to chops! We had a hard
>time explaining the damage to my stepmom. ;-)
> Once again, the GMCNet transports me back to happy memories of a
misspent
>youth! (As the rock singer Meatloaf says: "A wasted youth is better by far
>than a wise and productive old age!")
>
>Rick Staples
>'75 Eleganza
>Louisville, CO
>
Genef -- 77PB/ore/ca
GMC MOTORHOME INFORMATION
mr.erf
http://www.california.com/~eagle/
 
snip..........
>I do have a problem with my Onan. It does not
>consistently hold a constant voltage. Sometimes it
>runs just fine for hours and hours. Then all of a
>sudden it will decide to cycle between 90 volts and
>140 volts. It will do that for a while and then I'll
>worry that will wreck something, so I'll shut it down.
>The next time I run the Onan it will run just fine for
>a few hours.
Sounds like you have a faulty governor. That is my best mechanically
challeged opinion!
Dave Greenberg
Seasons Greetings To All!
 
Hi Glenn

The GMC trouble shooting chart says to check the fuse first.

If OK check for 12 volts between terminals1 and 10 If not 12V then the Start
solenoid is bad.

If OK jumper terminals 9 to 11. If engine starts it says to replace circuit
board because relay K2 has defective contacts. (seems a bit extreme..
replace the board not the relay) Jumpering 9-11 also bypasses the contact on
K3 to it could also be a bad contact on K3 (same extreme solution I presume)

Good Luck

Dave
 
> If OK check for 12 volts between terminals1 and 10 If not 12V then the
Start
> solenoid is bad.

OOPS Check for 12 volts while cranking, you could get cranky looking for
voltage here without having the starter engaged :-)

Dave
 
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