| Onan/Petronix ignition Ken H. [message #98610] |
Sun, 05 September 2010 07:23  |
fred v
Messages: 999
Registered: April 2006
Location: pensacola, fl.
Karma: 0
|
Senior Member |
|
|
Ken; John and i were doing this conversion to his Onan and on this page:
http://www.gmcmhphotos.com/photos/showphoto.php?photo=6804&cat=3608
you say to remove the wire from the + side of the coil to the points. on his the points were connected to the - side of the coil. 12 v + connects to the + side of the coil.
which way is correct?
we were unable to get the module to spark the plug lead. should the flat side of the module face the magnet or the 3 angle side of the module?
why do you ground one of the spark leads to test the set up?
thanks,
Fred V
'77 Royale RB 455
P'cola, Fl
|
|
|
|
| Re: Onan/Petronix ignition Ken H. [message #98611 is a reply to message #98610] |
Sun, 05 September 2010 07:30  |
fred v
Messages: 999
Registered: April 2006
Location: pensacola, fl.
Karma: 0
|
Senior Member |
|
|
sorry, the module John has is different from the one you show. his is flat on one side and angled on the other side. i could not see any difference in the magnet. it was just as strong on one side as the other. it was weaker on the thin edge sides but strong on the side face.
Fred V
'77 Royale RB 455
P'cola, Fl
|
|
|
|
| Re: [GMCnet] Onan/Petronix ignition Ken H. [message #98616 is a reply to message #98610] |
Sun, 05 September 2010 08:02 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
|
Senior Member |
|
|
Fred,
Picky, picky, picky!!! You're the first one to mention that in all the
years that album has been posted, and through all the dozens, if not more,
of Pertronix mods that have been done following it.
I suspect that everyone has done what really should be done: Disconnect the
ignition points lead, ignoring the polarity markings on the coil.
Theoretically, the points should be connected to the (-) lead.
Practically, with the "lost spark" connection of the Onan coil, it can't
matter. I suspect that the Onan on which we made the photos (Bobby
Moore's?) was wired as my photo caption says and I never before considered
the significance.
Thanks for finding that error (?).
As for the magnet, I was surprised when John said during one of our 4-5
conversations yesterday that there was no paint dot marking the "hot spot"
on the module. He eventually found it by inserting an indicator bulb in
series with the black lead of the module and passing a magnet over the
module. We had to have the discussion of that twice because the test light
illuminated as soon as he connected +12 VDC to the red lead -- that's as it
should be. Just like any other coil ignition, it fires when the points
OPEN.
The significance of the magnet's orientation is whether the North or South
polarity is toward the module. On at least one I installed that was
significant; it MAY not be on all -- Hall Effect Sensors are available with
N, S, and either sensitivity, IIRC.
Remember that the spark must jump the gaps of both spark plugs. When
neither is under compression, neither generates a bright enough spark to be
seen. Grounding the opposite plug in effect halves the distance the spark
must jump and seems, to me, to make it a little brighter. But every time I
seen an Onan spark I wonder how the darned thing can run -- it's VERY weak.
I'm confident the engine will run today. Don't hesitate to call if you need
help.
Ken H.
Ken; John and i were doing this conversion to his Onan and on this page:
> http://www.gmcmhphotos.com/photos/showphoto.php?photo=6804&cat=3608
> you say to remove the wire from the + side of the coil to the points. on
> his the points were connected to the - side of the coil. 12 v + connects to
> the + side of the coil.
>
> which way is correct?
>
> we were unable to get the module to spark the plug lead. should the flat
> side of the module face the magnet or the 3 angle side of the module?
>
> why do you ground one of the spark leads to test the set up?
> thanks,
>
> --
> Fred V
> '77 Royale RB 455
> P'cola, Fl
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
|
|
|
|
| Re: Onan/Petronix ignition Ken H. [message #98621 is a reply to message #98610] |
Sun, 05 September 2010 08:17 |
 |
mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
Karma: 0
|
Senior Member |
|
|
| fred v wrote on Sun, 05 September 2010 05:23 |
Ken; John and i were doing this conversion to his Onan and on this page:
http://www.gmcmhphotos.com/photos/showphoto.php?photo=6804&cat=3608
you say to remove the wire from the + side of the coil to the points. on his the points were connected to the - side of the coil. 12 v + connects to the + side of the coil.
which way is correct?
we were unable to get the module to spark the plug lead. should the flat side of the module face the magnet or the 3 angle side of the module?
why do you ground one of the spark leads to test the set up?
thanks,
|
I am not Ken. But I just did this modification. (And it is a good modification.)
Disconnect the points from the coil and tie it up out of the way. (Yes, it should have been on the negative side.) Connect the module across the coil. Red(+)/Black(-)
There are a couple of different modules (and MANY more mounting brackets) used in different applications. they all SHOULD work As long as it uses a magnet and the module is for a negative ground. (I think there is a way to use the "lobe sensor" style but as they cost more, I do not see the need.)
You have to have the magnet pass close to the same side of the module as in the intended application. Normally it will be the opposite corner from the mounting tab on the module. (Look at the instructions that came with the module.) They normally have a yellow dot to mark the corner with the sensitive area. But IIRC, the mark itself, is NOT on the sensitive area! It is on the side NEXT to the sweet spot.
NOTE 1: The yellow mark may not be accurate enough for setting the timing.
NOTE 2: If you have a different module, it might require a different bracket from the pictures posted on the web.
NOTE 3: Be careful not to touch the black lead to any positive source. My first one touched the positive side of the starter and blew the module right into the trash can! (I let the smoke out.)
I did not ground any of the spark leads when testing. I put spark plugs on the leads and had them on top. Moving the magnet next to the sensitive are would spark both plugs. I understand the orientation of pole of the magnet is important. I stuck it to the fly wheel, checked it, then glued it on the way that worked. I glued it a little "tall" on the fly wheel to ensure clearance of the other fins on the fly wheel.
Hope it helps.
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
|
|
|
|
| Re: [GMCnet] Onan/Petronix ignition Ken H. [message #98622 is a reply to message #98616] |
Sun, 05 September 2010 08:15 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
|
Senior Member |
|
|
Discussing the coil connections reminds me of a tale from Bean Station a few
years ago:
I was tinkering with someone's Onan, possibly installing a Pertronix. As I
left there I passed by the crowd of 5-6+ people around another one. At the
center of the crowd, receiving all kinds of suggestions, was probably the
most technically competent, long-time, GMCer in Dixielanders, who held both
ME and EE degrees from Ga. Tech.
He and his crowd of supervisors had done something to the Onan that required
disconnecting the coil temporarily. Now the Onan wouldn't run for nuthin'.
Having just moments before been looking at the wiring on a running Onan,
glance at the dead one and said, "Move that wire to the other side of the
coil." And walked away. I wasn't 25 feet away when I heard the engine
start.
My poor "indian" friend with all the "chiefs" around helping him (to not
think) was devastated; too embarrassed for words, 'cause he really hated
being wrong about anything -- it so seldom happened.
DARN I've been missing him for the past 5 years!
Ken H.
On Sun, Sep 5, 2010 at 9:02 AM, Ken Henderson <hend4800@bellsouth.net>wrote:
> ...I suspect that everyone has done what really should be done: Disconnect
> the ignition points lead, ignoring the polarity markings on the coil.
> Theoretically, the points should be connected to the (-) lead...
>
_______________________________________________
GMCnet mailing list
List Information and Subscription Options:
http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
|
|
|
|
| Re: Onan/Petronix ignition Ken H. [message #98632 is a reply to message #98610] |
Sun, 05 September 2010 10:06 |
fred v
Messages: 999
Registered: April 2006
Location: pensacola, fl.
Karma: 0
|
Senior Member |
|
|
thanks guys, i had to leave John at noon yesterday and we will get back together today and finish it up, hopefully.
Fred V
'77 Royale RB 455
P'cola, Fl
|
|
|
|
|
|
GMCforum
Search
Help
Register
Login
Home
