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Old 10-14-2016, 11:00 AM   #1
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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.
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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
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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!
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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
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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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Old 08-26-2017, 02:21 PM   #11
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I, too, have had DW ask if I attempted to start our 4KY spec K Onan. "Of course not." was my reply. Then as we sat on the couch discussing the issue I heard the generator attempt to start. Lifting the cover, it first sounded like the fuel pump was cycling. I attempted to start, no luck. I followed the trouble code process; result was Code 12... which by all accounts "required" Onan service. I was finally to start the generator, it ran well under load of AC. But when I attempted to stop from interior, it continued to run. I then attempted to stop using the main switch; same result. The only way to stop the generator was to disconnect the 12v power cord. After lots of reading, checking oil and fuel levels, cleaning the connectors, ensuring a good ground, I called the Onan distributor in Boise. (We were traveling at the time.) He suggested an appointment at $125/hr. for diagnosis, also saying it could take up to 2 hrs. I was skeptical. I had replaced a control board and regulator on an older unit with Flight Systems, so I began to read more on the newer 4KY issues. I ordered their new "Made in USA", exact fit, control board from PartsForTechs.com (said to be reversed engineered with larger heat sink) from ASAP as a replacement. At $329, it seemed reasonable. It installed in about 15 minutes and and suddenly all was terrific... it starts (and stops) immediately from both main and auxiliary switches. All's good and I saved hundreds of $$$.
...keep a set of spare keys handy! '08 Sightseer 29R ('07 chassis 18K chassis); SCT Tune; Banks; RM sway bars; SS trak bar; Sumos; 480W GoPower; '10 CR-V toad
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Old 08-26-2017, 02:39 PM   #12
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Hi John! Welcome to IRV2! We're sure glad you joined the gang!

Hope your problem turns out to be a simple one! Keep her between the ditches!

Good luck, happy trails, and God bless!
Joe & Annette

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Old 08-26-2017, 04:02 PM   #13
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I will mention that the amount of leakage to start some of these generators is very small indeed. I once accidentally connected a device to the start line on my set and it started right up! (Though I was connecting between 12V and ground...)
My name is Peter, and I'm never going to grow up.
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Old 08-26-2017, 04:13 PM   #14
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Yep, moisture can get into one of the connectors and cause this. And, as was posted earlier, most propane gemerators run off the liquid port not the gas port.
I had my 12.5 diesel Onan start one day, but I had inadvertently set the "exercise" option in the Silverleaf whole house control.

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