| Onan Cranking Current. [message #310204] |
Thu, 10 November 2016 14:23  |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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About Onan cranking current.
Quick answer:
152 Amp peak
91 Amp RMS
There was recently some discussion about this and I happened to have:
This all about a BF (4.0) Onan. I don't know how it would relate to and NH (6.0).
A - An Onan start switch close to the Onan's battery (its a 23).
B - My instrument case in the coach for several reasons.
C - Time to do this experiment.
So, I have an 87 and Bell probe (they are both old, but still good) and I put the probe on the power to the Onan and set the Fluke up to capture. It was cold enough that I hoped the Onan. I got two good 3~5 second cranks before it started.
This was in about 50° weather and with a nice running BF that has had 10-30 Mobil 1 in it as long as I have owned it.
The Onan's battery was new two years ago.
So, if you care, you have that for a data point.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: Onan Cranking Current. [message #310207 is a reply to message #310204] |
Thu, 10 November 2016 14:34  |
lqqkatjon
Messages: 2324
Registered: October 2010
Location: St. Cloud, MN
Karma: 5
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Senior Member |
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Thanks Matt. that is very helpful information.
Jon Roche
75 palm beach
EBL EFI, manny headers, Micro Level, rebuilt most of coach now.
St. Cloud, MN
http://lqqkatjon.blogspot.com/
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| Re: [GMCnet] Onan Cranking Current. [message #310219 is a reply to message #310204] |
Thu, 10 November 2016 20:47 |
Jim Miller
Messages: 501
Registered: March 2008
Karma: 10
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Senior Member |
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Hi Matt,
The peak value is a good reference point but the RMS value doesn’t hold much relevance on a DC circuit since RMS is really only meaningful on periodic signals such as those found in AC circuits.
Do you know the condition of your starter - as in how long ago it might have been rebuilt? The misbehaving Onan starters that we’ve worked on at the Miller compound almost universally have had a worn out nose bearing that results in substantial current draw but minimal cranking enthusiasm. Some owners were attributing the starter’s lethargy to bad batteries, wiring problems, solenoid issues etc but all it turned out to be is a bronze bushing that costs less than a dollar and takes only a few minutes to replace once the starter is off the machine. I would never have guessed that a sleeve bearing that was worn only a slight amount could result in this situation but if one thinks about the radial load on the starter’s armature during starting then I guess it makes sense.
Thanks for posting your measurements!
--Jim Miller
1977 Eleganza
1977 Royale
Hamilton, OH
> On Nov 10, 2016, at 3:23 PM, Matt Colie wrote:
>
> About Onan cranking current.
>
> Quick answer:
> 152 Amp peak
> 91 Amp RMS
>
> There was recently some discussion about this and I happened to have:
> This all about a BF (4.0) Onan. I don't know how it would relate to and NH (6.0).
> A - An Onan start switch close to the Onan's battery (its a 23).
> B - My instrument case in the coach for several reasons.
> C - Time to do this experiment.
>
> So, I have an 87 and Bell probe (they are both old, but still good) and I put the probe on the power to the Onan and set the Fluke up to capture. It
> was cold enough that I hoped the Onan. I got two good 3~5 second cranks before it started.
> This was in about 50° weather and with a nice running BF that has had 10-30 Mobil 1 in it as long as I have owned it.
> The Onan's battery was new two years ago.
>
> So, if you care, you have that for a data point.
>
> Matt
> --
> Matt & Mary Colie - Members GMCMI, GMCGL, GMCES
> '73 Glacier 23 - Still Loving OE Rear Drum Brake with Applied Control Arms
> Now with both true Keyless and remote entry
> SE Michigan - Twixt A2 and Detroit
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
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Jim Miller
1977 Eleganza II
1977 Royale
Hamilton, OH
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| Re: Onan Cranking Current. [message #310265 is a reply to message #310204] |
Sat, 12 November 2016 07:18 |
Steve
Messages: 506
Registered: September 2013
Location: East Greenville, Pa
Karma: 1
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Senior Member |
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A little off topic, but just for the record, Jim Miller saved my Onan nearly 3 years ago when I was new to this group. Many thanks to Jim and others who have helped with numerous items. Jim = Onan Rock Star!
1978 GMC Royal
Eastern Pennslyvania
1968 Chevrolet C20 396 Camper Special
1969 Chevrolet C20 Camper Special
1985 Buick Electra Park Avenue
1992 Camaro 25th Anniversary Heretage Edition Black
[Updated on: Sat, 12 November 2016 07:19] Report message to a moderator |
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| Re: Onan Cranking Current. [message #310276 is a reply to message #310204] |
Sat, 12 November 2016 16:53 |
JohnL455
Messages: 4447
Registered: October 2006
Location: Woodstock, IL
Karma: 12
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Senior Member |
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They can be made into truely finger tip starting units, by simply catching up with the years of neglected maintenance compounded by age and environment. Mine was an instant start every time on our last 2 week trip in mostly cold weather. All stock no fuel pump pre run button.
John Lebetski
Woodstock, IL
77 Eleganza II
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