Onan 6K coil replacement

jack ramsey · Jul 30, 2018

things going well and thought a proactive replacement of a 43 yr old coil might help (some hard starting when hot) and got a J&P coil. Long story
short, really did not fit. It is shorter and has a larger diameter than the original. I ground out the diameter issue and THINK I can make it work by
sliding it up a couple of inches and using a longer screw on the metal clamp, just might make it fit and not have to rewire it. I did add the Bovee
pointless ignition a few months ago and cold start is really good. runs well and I start it practically every week to keep things operational. May
just order a coil from Jim K, for I do like things tidy. Concerned it might not be a clean "clamp".

Do I need to also replace the capacitor between the positive coil terminal and ground while I have it out?

http://www.gmcmhphotos.com/photos/electrical/p65050-onan-coil-replacement.html

http://www.gmcmhphotos.com/photos/electrical/p65049-onan-coil-replacement.html

http://www.gmcmhphotos.com/photos/electrical/p65048-onan-coil-replacement.html

Thanks!

Jack
--
Jack Ramsey
Tulare, CA
TZE165V101526
1975 Palm Beach

Ken B · Jul 30, 2018

I have never see the stuff that Bovee sells. I am assuming that he is ordering Pertronix units and repackaging them under his name. If so, then I am
familiar with the Pertronix units that we have been installing on GMC Onans for many years.

The capacitor / condenser installed on the positive side of the coil is for radio ignition noise suppression. You can run with it, or without it. I
have never seen one fail but it would only have 2 failure modes:
1. Shorted - which cause the fuse to blow on the Onan board.

2. Open - which might cause spark plug noise in your radio.

I would not mess with it my self. I do not know if I have one on my Onan or not.

A comment on Onan coils. Last year I ordered a new genuine Onan coil for a coach that I was working on. Upon receiving it I found that the primary
side measured considerably higher resistance and it would not run. I had to change the Dwell on the points to get it to run reliably. I do not know
how it affects the Bovee you are running.

You might measure the old and new coils both primary and secondary side and see if they are the same.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

thomas phipps · Jul 30, 2018

Concur with Ken Burton. Once you have a pointless or HEI replacement ignition system, the condenser is just along for the ride. Disconnect it, remove
it, leave it alone - it is no longer in the working ignition circuit. It is only needed if you are still using the points as an ignition trigger. As
Ken says, main purpose is ignition noise (RF) out of your radio. Side benefit is extends the life of the ignition points.
You might consider leaving it installed, if you have left the points installed if you left the OEM system installed for possible module failure. Would
only have to move one wire to return to original design.
It is possible to install a modern CDI system that still uses the original points to provide the trigger. Kit costs about $25. But you would still
have the 'wandering' of the original point design. Better to go with a pointless system.
Tom

--
2012 Phoenix Cruiser model 2552
KA4CSG

LQQKatJon · Jul 30, 2018

Strange. I will have to take a photo when I get a chance on the harley coil I installed last fall. About 5 minutes of hand filing of the clamp and
it fit perfectly.

--
Jon Roche
75 palm beach
St. Cloud, MN
http://lqqkatjon.blogspot.com/

bill wevers · Jul 30, 2018

I've been running the Harley coil for 5 years.
It's a snug fit.

--
Bill Wevers GMC49ers, GMC Western States
1975 Glenbrook - Manny Powerdrive, OneTon
455 F Block, G heads
San Jose

jim miller · Jul 30, 2018

> Concur with Ken Burton. Once you have a pointless or HEI replacement ignition system, the condenser is just along for the ride. Disconnect it, remove it, leave it alone - it is no longer in the working ignition circuit. It is only needed if you are still using the points as an ignition trigger. As Ken says, main purpose is ignition noise (RF) out of your radio. Side benefit is extends the life of the ignition points.

I think there are two different “condensers” being discussed and confused here. I believe the original topic was about the RFI suppressor that looks like a condenser and is mounted immediately adjacent to the coil. This device (not necessarily a condenser - but more akin to a RF filter) serves to snub the electronic noise that would scramble every AM radio from here to Alpha Centauri. Can anyone say “spark gap transmitter”? I concur with everyone that says that it serves no purpose in the present day and can only serve as a threat if it were to fail shorted.

On the other hand the true ignition condenser is mounted immediately adjacent to the points inside the points enclosure and serves two purposes that are equally important - 1. it quenches the spark generated at the time the points open so as to prevent undue erosion of the contacts, and 2. it serves as the C in an LC tank circuit formed along with the primary of the coil serving as the L. The presence of the parallel tank circuit serves to capture and reflect as much energy as possible back into the coil as the instant the magnetic field collapses and thus drives that energy toward the secondary and the spark plugs.

It is my belief that the capacitance of the condenser is somewhat intentionally matched with the impedance of the coil primary so as to maximize the effectiveness of the resonant circuit - and thus drive as much energy as possible toward the secondary as soon as the points go open after the dwell charge time. Having a mismatched coil and condenser may not work well as Ken described due to the loss of the contribution from the LC tank. Considering that the spark plugs are already in series with one another and each therefore gets only half of the secondary voltage, _any_ loss of energy out of the primary side can cause poor (or no) ignition.

I did some research on the shallow plastic Onan coils that work as direct replacements for the original deep-can coil. There are two models of coils that appear identical to one another yet differ in their electrical characteristics - and Onan specifies one of them for points-ignition machines and the other one for electronic ignition units. I expect the difference is in the inductance of the primary winding; I’ll have to get one of each in the electronics lab and probe them to discover their secrets. While at it I may tear the RFI filter off of my Onan and run the network analyzer on it to see what it really does - if it does anything at all after 40 years.

—Jim

Jim Miller, N8ECI
1977 Eleganza
1977 Royale
Hamilton, OH

Ken B · Jul 31, 2018

Hi Jim,

I did not discuss the condenser in my posting because he specifically said he was not using points. I was assuming the Bovee system was a
re-marketed Pertronix.

The condenser / capacitor I was specifically discussion was the RFI one.

Thanks for the very detailed response.

Ken B.
--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

robert mueller · Aug 2, 2018

G'day,

Gary copied my Pertronics installation (I was flattered):

http://www.gmcmhphotos.com/photos/g5435-onan-pertronix-ignition.html

Applied sells them:

http://www.appliedgmc.com/prod.itml/icOid/1504

Here's Applied's coil:

http://www.appliedgmc.com/prod.itml/icOid/1418

I would suggest you ask if it fits perfectly.

Seems to me a bit of work with a Dremel would make the JP Cycles coil fit just fine.

--
Regards,
Rob M. (USAussie)
The Pedantic Mechanic
Sydney, Australia
'75 Avion - AUS - The Blue Streak TZE365V100428
'75 Avion - USA - Double Trouble TZE365V100426

jack ramsey · Aug 4, 2018

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Onan 6K coil replacement

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