| Onan fix [message #202198] |
Tue, 19 March 2013 20:58  |
Chr$
Messages: 2690
Registered: January 2004
Location: Scottsdale, AZ
Karma: 1
|
Senior Member |
|
|
Folks, I came up with a fix for an Onan that will only start when you temporarily jumper 5-9 on the control board. I ran a wire through a diode from 9 to the starter solenoid. This way, pin 9 gets 12V as soon as you hit the start switch and then it disconnects when you let go of the start switch. The diode blocks the DC voltage from pin 9 back feeding to the solenoid once it is running, as Pin 9 has 12V to run the fuel pump after K2 pulls in when running.
Seems to work. I used a 3A Diode.
A relay would also work with the starter solenoid power energizing the relay.
With this setup, all the regular LOP and engine safety items still work.
My onan fires right up now.
Comments?
-Chr$: Perpetual SmartAss
Scottsdale, AZ
77 Ex-Kingsley 455 SOLD!
2010 Nomad 24 Ft TT 390W PV W/MPPT, EV4010 and custom cargo door.
Photosite: Chrisc GMC:"It has Begun" TT: "The Other Woman"
|
|
|
|
| Re: [GMCnet] Onan fix [message #202201 is a reply to message #202198] |
Tue, 19 March 2013 21:20  |
Mr ERFisher
Messages: 7117
Registered: August 2005
Karma: 2
|
Senior Member |
|
|
why does it need the mod?
gene
On Tue, Mar 19, 2013 at 6:58 PM, Chris Choffat <cchoffataz@yahoo.com> wrote:
>
>
> Folks, I came up with a fix for an Onan that will only start when you
> temporarily jumper 5-9 on the control board. I ran a wire through a diode
> from 9 to the starter solenoid. This way, pin 9 gets 12V as soon as you hit
> the start switch and then it disconnects when you let go of the start
> switch. The diode blocks the DC voltage from pin 9 back feeding to the
> solenoid once it is running, as Pin 9 has 12V to run the fuel pump after K2
> pulls in when running.
>
> Seems to work. I used a 3A Diode.
>
> A relay would also work with the starter solenoid power energizing the
> relay.
>
> With this setup, all the regular LOP and engine safety items still work.
>
> My onan fires right up now.
>
> Comments?
>
> --
> -Chr$: Perpetual SmartAss
> Scottsdale, AZ
> 77 Ex-Kingsley Featuring: 455, Power Drive, 3:21, Rockwell, Jim B QJET,
> Qbag. Now for Sale
> 2010 Nomad 24 Ft Travel Trailer
>
> Photosite: Chrisc "It has Begun"
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Gene Fisher -- 74-23,77PB/ore/ca
“Give a man a fish; you have fed him for today --- give him a URL and
-------
http://gmcmotorhome.info/
Alternator Protection Cable
http://gmcmotorhome.info/APC.html
_______________________________________________
GMCnet mailing list
Unsubscribe or Change List Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
|
|
|
|
| Re: Onan fix [message #202220 is a reply to message #202198] |
Tue, 19 March 2013 23:29 |
Chr$
Messages: 2690
Registered: January 2004
Location: Scottsdale, AZ
Karma: 1
|
Senior Member |
|
|
Cuz its broke and I don't want to take it apart to replace the regulator that supposedly energizes the fuel pump at startup.
It's a quick fix for an over-engineered half assed control system.
-Chr$: Perpetual SmartAss
Scottsdale, AZ
77 Ex-Kingsley 455 SOLD!
2010 Nomad 24 Ft TT 390W PV W/MPPT, EV4010 and custom cargo door.
Photosite: Chrisc GMC:"It has Begun" TT: "The Other Woman"
|
|
|
|
|
|
| Re: Onan fix [message #202249 is a reply to message #202198] |
Wed, 20 March 2013 09:24 |
Chr$
Messages: 2690
Registered: January 2004
Location: Scottsdale, AZ
Karma: 1
|
Senior Member |
|
|
Ok here's a better one. The problem was intermittent, so in testing the unit using the various procedures out there, the 5-9 jumper worked every time. I just made a permanent version of it that is in the circuit when you need it, and out when you don't.
-Chr$: Perpetual SmartAss
Scottsdale, AZ
77 Ex-Kingsley 455 SOLD!
2010 Nomad 24 Ft TT 390W PV W/MPPT, EV4010 and custom cargo door.
Photosite: Chrisc GMC:"It has Begun" TT: "The Other Woman"
|
|
|
|
| Re: Onan fix [message #202267 is a reply to message #202249] |
Wed, 20 March 2013 12:02 |
Carl S.
Messages: 4186
Registered: January 2009
Location: Tucson, AZ.
Karma: 13
|
Senior Member |
|
|
| Chr$ wrote on Wed, 20 March 2013 07:24 |
Ok here's a better one. The problem was intermittent, so in testing the unit using the various procedures out there, the 5-9 jumper worked every time. I just made a permanent version of it that is in the circuit when you need it, and out when you don't.
|
Chris,
That sounds like a good solution to me.  Thanks for sharing it. It may be kind of a unique condition that you addressed, but I'm sure it will apply to other people's Onans as well.
Carl Stouffer
'75 ex Palm Beach
Tucson, AZ.
Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member
|
|
|
|
| Re: Onan fix [message #202288 is a reply to message #202198] |
Wed, 20 March 2013 18:16 |
 |
mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
Karma: 0
|
Senior Member |
|
|
| Chr$ wrote on Tue, 19 March 2013 18:58 |
Folks, I came up with a fix for an Onan that will only start when you temporarily jumper 5-9 on the control board. I ran a wire through a diode from 9 to the starter solenoid. This way, pin 9 gets 12V as soon as you hit the start switch and then it disconnects when you let go of the start switch. The diode blocks the DC voltage from pin 9 back feeding to the solenoid once it is running, as Pin 9 has 12V to run the fuel pump after K2 pulls in when running.
Seems to work. I used a 3A Diode.
A relay would also work with the starter solenoid power energizing the relay.
With this setup, all the regular LOP and engine safety items still work.
My onan fires right up now.
Comments?
|
Good work-a-round Chris!
Now looking at the problem that you have worked around....
Symptom: The Onan would not start without a jumper but would stay running after the jumper was removed. (If started with the jumper.) ... Correct?
Using a diagram of the Onan control board, lets look at theory:
1. The Onan needs power on pin 9 to run.
2. Pin 9 gets its power from the fuse through an energized K3 relay.
3. K3 is energized, while running, from K2 being held energized by the rectified AC voltage from the flywheel alternator (pins 5 and 8.) To do this, K2 passes voltage from the fuse through CR7 and R2 to the coil of K3.
4. The power to keep K3 energized is lost when ground is applied at pin 12 by the oil pressure switch. This is the oil safety circuit. (There seems to be a lot of excess circuitry for this... I expect there was something else designed to be connected there.)
5. The power to keep K3 energized is also lost when ground is applied at the coil of K3 by S3 or the generator remote switch. IE: Pressing "stop."
6. NOW When starting, there is no AC voltage to energize K2. The power to energize K3 has to come from somewhere differently... just when starting. So where would it come from? From the relay that controls the starter solenoid -- K1. This is the relay that looks like a old style Ford starter solenoid. There should be a wire from this "solenoid" to pin 10 to apply power through CR5 and R2 to K3 and energize it.
SO.....
Looking at the diagram, noting what is working fine while running, (like R2 and K3) the problem with your Onan looks to be from K1, the wire to pin 10, CR5 to R2.
Not much to check it you feel like looking... 
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
[Updated on: Wed, 20 March 2013 18:17] Report message to a moderator |
|
|
|
GMCforum
Search
Help
Register
Login
Home
