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A Bad Onan kind of day!


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  #1  
Old 04-10-2017, 01:32:01 PM
GMGuy GMGuy is offline
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Default A Bad Onan kind of day!

What are the chances, 2 Onans and no power. One wouldn't start and the other appears to have a bad Voltage Regulator.

So, Friday, I went up to my cottage 2 hours from the city to find a late season snowfall had taken the power out. No problem, I thought, I have my recently acquired JB 7.5 (705JB-3R/1P ser36C874768) I had run it 36 hours straight at Christmas without issue. I go to start it, and the battery is down in charge, so it wouldn't roll over. I then got a spare battery and it rolled over well, and fired intermittently on one lung, but would not catch. I could not get it to run, and didn't want to burn up the starter.
It was now getting dark, so I rolled out the Model 5.5 BGM F A 26105 H (Ser 0000 092795) Marquis 5500, and it fired right up. I haven not used it in a bit, so I took a meter just to check (better safe than sorry), and 60Hz, but over 200V at no load (yikes). Glad I checked, because I don't know how many things would have appreciated that over-voltage. 2 down....

On the up side, the power was restored just an hour later. I now have to diagnose the no-start and the likely bad voltage regulator.

Oh well, just another day, and the beer was still cold!

Ralph
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Old 04-10-2017, 01:50:46 PM
len k len k is offline
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Default Re: A Bad Onan kind of day!

Can always put the beer in the snow

Guessing fuel starvation on the JB, try squirting some gasoline down the carb to see if it will start. I've test run my JB on steady FINE THIN stream of gasoline from a squirt bottle down the carb ( ~ 1/32 inch dia, and even then had to stop squirting sometimes). IF runs check for gas flow to carb and clean the carb. Ethanol in gas gums up carb if it sits for several months.

BGM .... odd that it went to overvoltage, reg usually dies and it goes to 1-2 VAC. You might have gotten lucky and caught it before $270 reg died. Try cleaning the slip rings with scotchbrite pad. Lot of times they oxidize and get high contact resistance then kill the AC voltage reg. Takes bunch of months , maybe > 6, but I've measured 100 ohms between the brushes after ~ 3-4 months of sitting. Should be 20.25-24.75, (30 max.), with reg unplugged, engine off.

Last edited by len k; 04-10-2017 at 02:01:12 PM.
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Old 04-10-2017, 02:28:32 PM
GMGuy GMGuy is offline
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Default Re: A Bad Onan kind of day!

Won't be up until Friday, but will check them both, thanks Len!
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Old 04-10-2017, 02:50:30 PM
LRomero LRomero is offline
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Default Re: A Bad Onan kind of day!

A bad Onan day is still better than a good day at the office.
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Old 04-11-2017, 07:45:55 AM
GMGuy GMGuy is offline
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Default Re: A Bad Onan kind of day!

I have to agree with that comment any day!!!

So, I did a little reading in the Marquis 5500 manual in the troubleshooting section and it says that if the frequency is correct (ie, the right RPM), but the voltage is high, then it is a failed Voltage Regulator.
I know Len, you said check the slip rings, but I would suspect that would result in a low voltage, not high.
I am thinking I will need a new voltage regulator.
Mr. Onan Parts, do you know if they are available and about how much?

Thanks
Ralph
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Old 04-11-2017, 08:16:52 AM
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Billy J Shafer Billy J Shafer is offline
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Default Re: A Bad Onan kind of day!

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Originally Posted by LRomero View Post
A bad Onan day is still better than a good day at the office.
Or working on a Genajunk unit.
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I don't talk to myself. This early in the morning. Why the hell should I talk to you.
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Old 04-11-2017, 08:58:34 AM
LRomero LRomero is offline
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Default Re: A Bad Onan kind of day!

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Or working on a Genajunk unit.
Amen to that.
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Old 04-11-2017, 10:34:34 AM
len k len k is offline
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Default Re: A Bad Onan kind of day!

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I know Len, you said check the slip rings, but I would suspect that would result in a low voltage, not high.
Clean the slip rings anyways and try it. In my testing I found resistance varies around the slip ring, might confuse the reg.

Cleaning slip rings fixed the problem for other people that had voltage. I seem to remember one person that had high voltage......I think.
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Old 04-11-2017, 10:37:19 AM
GMGuy GMGuy is offline
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Default Re: A Bad Onan kind of day!

I will try before I buy!!!!
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Old 04-11-2017, 12:47:32 PM
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OnanParts OnanParts is offline
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Default Re: A Bad Onan kind of day!

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I will try before I buy!!!!
If cleaning the slip rings does not work..

http://www.flightsystems.com/p-ONAN-305-0826.html
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