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Old 10-14-2016, 11:00 AM   #1
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Join Date: Aug 2015
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Onan Generator Started by itself & wouldn't turn off

I woke up this morning to my wife frantically calling out "come quick --the motorhome is running--thieves are stealing it". The 1999 37 ft Harney Diesel pusher is parked in our driveway and is blocked in by my pickup. I knew if it was being stolen they weren't going anywhere. I have to admit that for a second the thought of it disappearing was a relief as we are ready to upgrade. Sure enough when I got to the garage to put on my rain coat, I could hear the propane Onan generator purring away.

Hence began the saga of "What the heck"?
1.) It is not equipped with auto-start
2.) It is plugged into a 50 AMP outlet in the garage and had plenty of power.
3.) I have a trickle charger plugged into the batteries and they were fully charged.
4.) When I attempted to turn it off from both switches. It would only bang, rattle, backfire, and then continue to run as soon as I took my finger off of the kill switch. I am surprised my neighbors didn't call the police as each backfire (at 6:30 AM) sounded like a high caliber rifle shot.

Now I was beginning to panic. I had a full tank of propane so it would run forever. Please note turning the propane valves off did not kill the generator - I am not sure why. I tried everything electrical thinking that something was telling it to run. I unplugged it from the 50 Amp outlet, turned the inverter off, shut of the battery connection, reset all the breakers but she just kept on purrring away.

I do not give up easily. In my 60 plus years of life I have never been outwitted by a machine and this was not going to be my first. I discovered that if I held the throttle linkage closed it would cut off the supply of fuel. However when it died, it would still try to restart. I knew that if I interrupted the flow of 12 volt electricity from the battery it wouldn't be able to start again. That was easier said than done. Did I mention it was raining and access to the lead from the battery was very difficult. I was running out of options as she defiantly purrred on. I decided to disconnect any wire I could reach that directly attached to the generator. I got my voltage tester and started poking wires to make sure I didn't get lit up like a Christmas tree. As I poked around I found a wiring harness with about 10 prongs. I unplugged it and she kept on purring . Next I pushed to throttle linkage to the left cutting off the fuel. She died!! This time no restart. I reluctantly stood there in the rain for about 10 minutes waiting for her to restart. Victory!!! Well kind of. I haven't tried to restart it yet because I fear the vicious cycle will continue. I am pretty sure if I need it I can start it at the gen set.

Ultimately I think that moister (did I mention it was frickin raining) got into the harness or control cable and did something. I will wait until after a stretch of dry weather to plug the wiring harness back in.

Wish me luck!!

John in Wet Washougal, Washington

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Old 10-14-2016, 11:33 AM   #2
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What is the model gen? Just curious is the remote switch sticking ? Hope you have dried off by now.

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Old 10-14-2016, 11:51 AM   #3
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I had a 7.5KW onan Gas that did same thing in rain. Disconnected battery supply and dried out Electronics in control box with hair dryer. Hooked up battery and all OK. Mine did this about 11 PM one night pouring down rain. No fun.
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Old 10-14-2016, 11:59 AM   #4
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I don't know about the gas model but the 7.5 diesel generator has a connection a foot or so from the generator and when/if it gets moisture in that connector the generator will self start. Similar to what ChasL mentions in the above post.
Bob, Sandi & Marmaduke the Big Pug
SW OREGON 2004 Journey 39K, 330 Cat
If towing: a 2006 Mini Cooper or 1995 Wrangler
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Old 10-14-2016, 12:09 PM   #5
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Same thing happened to my onan 7.5 desiel, when it was raining. I was able to shut it down without any trouble. Good luck
1998 National RV
Tradewinds 7370
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Old 10-14-2016, 12:43 PM   #6
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My harney has a disconnect in the battery tray. Maybe that was added later. Killing the propane will kill it after a minute or two of running. But beware, there are two valves. One for liquid and one for vapor. I believe our generators run off of liquid. The nice thing is that all of your appliances will continue to run even though you have the source to the generator killed.
Very strange indeed though. The harness you unplugged I would assume was the remote. That's where I would start too. But if it is running already, unplugging the harness won't kill it. It will just prevent it from starting again if the fault is in the remote.
I would love to have some Harney talks with you. There aren't many of us!
1999 Harney Renegade
Used mostly for weekends at the dragstrip with my rear engine dragster and my son's jr dragster.
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Old 10-15-2016, 12:28 PM   #7
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Onan gen ghost

It worked by unplugging the cable at the generator. The rain has not stopped and probably won't until about May. I have not worked on it yet. I am almost certain that it is a moisture issue. The big question is why? We are in the throws of putting some lipstick on the pig (I mean that in a kind way). The blue carpet is half way out, we are preparing to put wallpaper up, get rid of the fabric around the windows, tile the floor, refinish the table..... I am sure you get the picture! Anyway my point is that we have not used it for about a month. Even though we have had torrential rain the control switch and cable should be dry. It is anyone's guess.
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Old 10-15-2016, 03:33 PM   #8
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Get yourself a propane shut off valve that works, could be a major problem on it's own.
DaveB, Raleigh, NC
2015 Tiffin RED 33AA
2014 Honda CRV
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Old 10-15-2016, 03:44 PM   #9
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This is no help but I found it funny .
The very next post is " on an generator shut off & now won't restart "
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Old 10-16-2016, 06:51 AM   #10
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Off topic I know...but overall I have liked our Harney. But being a 17 year old coach means that things are getting dated.
Things that I think were a shortcoming for these coaches are the slide seal system....most of the industry uses an overlap exterior which I think is more reliable. They also used an aluminum exterior, which has had a terrible problem with galvinazation or whatever scientific name that corrodes the skin. But everything else I have really liked.

1999 Harney Renegade
Used mostly for weekends at the dragstrip with my rear engine dragster and my son's jr dragster.
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generator, onan

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