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Old 08-23-2019, 06:33 PM   #1
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ONAN quiet Diesel 7500

my neighbor has a tiffin pheaton and the genny just stopped. it was running then it just shut down. He told me over the phone no flashes or codes.
so when he gets home, we try to start it and it just turns over, never catches or sputters. we look in the coolant tank and it has a large amount of blackish oil.


me being an engine guy forever, thought the head gasket had failed .


he calls a certified onan tech and he says the magnet has thrown off the rotor in the generator module. and it has lost its oil into the coolant system.
this seems very ODD.
i was unaware the coolant flowed through the rotor and stator for the generator part.
so every one he has called say the ENTIRE unit must be replaced and there is no replacement module for the actual electricity generating parts, which i find to to be very ODD.


i can see the electricity portion as a separate unit online, so why or how or is the this the truth he needs to fork out 11k for a complete unit??
thanks
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Old 08-24-2019, 04:19 AM   #2
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I’m certainly no expert, but I have bled cash this year on an Onan 7.5 repair to the tune of $5100.00. I had to replace the rotor, stator, and inverter.

There are a couple of things in your post that don’t make sense to me.

1. There should be codes thrown when it shuts down.

2. Oil in coolant is not related to magnets being thrown. I’ve seen the rotor and stator removed, and there is no oil involved anywhere. If there is truly oil in the coolant, I don’t see how it is related to the rotor/magnet issue.

The 7.5 HDKAJ is notorious for throwing magnets and grenading the generator module. Supposedly Onan was “experimenting” with manufacturing brushless generators and found that the rotors had a tendency to throw magnets. That idea died and later models have brushes.

Your friend needs to bite the bullet and take his unit to a good shop and have them diagnose the problem. It won’t be cheap.
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Old 08-24-2019, 09:41 AM   #3
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Originally Posted by USMCRET View Post
Iím certainly no expert, but I have bled cash this year on an Onan 7.5 repair to the tune of $5100.00. I had to replace the rotor, stator, and inverter.

There are a couple of things in your post that donít make sense to me.

1. There should be codes thrown when it shuts down.

2. Oil in coolant is not related to magnets being thrown. Iíve seen the rotor and stator removed, and there is no oil involved anywhere. If there is truly oil in the coolant, I donít see how it is related to the rotor/magnet issue.

The 7.5 HDKAJ is notorious for throwing magnets and grenading the generator module. Supposedly Onan was ďexperimentingĒ with manufacturing brushless generators and found that the rotors had a tendency to throw magnets. That idea died and later models have brushes.

Your friend needs to bite the bullet and take his unit to a good shop and have them diagnose the problem. It wonít be cheap.



yep zero flashing codes, that what confused me as well.
when it turns over to start it just spins normally, with no odd noises. tail pipe is normal black and not wet.


i tried to get it to fire numerous times and it just spins, with no desire to fire.


i could not find any thing to indicate the rotor and stator module had any fluid involved as per the tech.


I did advise last night to call onan direct and get some input and find another tech that is certified. we are smack dab in the middle between shreveport LA and Dallas TX. lots of oil rigs and lots of cummins power generation people. SO he is going to try to get in at one of those places.


i was over the top confused about a complete replacement at 11k dollars, i asked..what about core charges or refunds on the kabota engine?


needless to say my neighbor was frazzeld when they got home.
100F outside, dash ac quit, no roof top ac and then a big hunk of steel rod through the front tire only miles from home.


so i did what we do and calmed them with knowledge and a plan to get tire replaced at home and go forward with lots of phone calls to find a good onan place to take the bus.
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Old 08-24-2019, 09:57 AM   #4
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One more small piece of info: When mine went, it would fire up but shut down within a second or two, and it always threw a code.

It may be worth the effort to retrieve the last code thrown by the unit. If the unit isn’t firing, it may not throw a code, but the last one thrown is always retrievable. This link tells how to do that:

http://www.tiffinrvnetwork.com/crusingator/P/P-049.pdf
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Old 08-24-2019, 12:09 PM   #5
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This reminds me of one time I had Speedco do the routine service and they filled the coolant reservoir with engine oil! Fortunately I found it before running the generator. They sucked the oil out and refilled it with coolant. I called Onan and they said it should be OK!
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Old 08-24-2019, 12:53 PM   #6
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this morning the coolant tank smells of FUEL
more than oil.

but he has a monady appointment at a reputable dealer so we shall see hopefully
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Old 08-27-2019, 09:02 AM   #7
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bing bang we have a diagnosis.
head gasket or cracked head, have to pull head and have it mag particle inspected.


so he is looking at 2k vice 11k





still puzzled why the onan super tech insists on a whole new unit?


in about 3 weeks we shall see if its right.


so she sits in the hangar awaiting her turn
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Old 08-27-2019, 08:11 PM   #8
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First off, NOT ALL the Onans with the magnets threw them off. I know several friends with them that have thousands of hours on them and not one has thrown a magnet. But, on the other hand, ours did with right at 105 hours on it. Also, when mine threw it, (which I had absolutely zero indication it did), it was still putting out 120VAC. I'd ran it like that for quite a while. Then, on a camp trip, we pulled into Bishop CA and, it was 100 degrees outside so, we fired up the genny.

WE turned the basement air on and all was well, FOR ABOUT 5 MINUTES! Then, the genny shut down. I had no idea there were codes then. A buddy that was traveling with us, informed me of the codes. Well, mine were 33. I re-started that genny several times and put the air on. Each time, it would run about 5 minutes and shut down. CRAP! So, we found a campground that wasn't crowded and setup for the night.

Now, my gen slides out on a tray so, getting to things is not bad at all. We yanked the top panel on that genny and found what looked like dark grey hair all over the place. And, it had also what looked like grey rocks stuck to all the metal surfaces. Hmmmmm. Well, long story short, the reason for the genny shut down was the infamous temp sensor had gone south for the winter. And the grey hair and rocks, was magnet pieces spewn all over.

I got the coach home, yanked the whole front end off the genny and saw that one of the magnets was missing. There was damage to the stator but, I felt not enough to replace. So, I got lucky and found an Onan 8000 watt rotor on ebay for $200. I had it shipped home to us. As for the temp sensor, well, that's a whole nother WW III story. It fought me all the way out.

But, I eventually got it all back together and it was working fine. But, I always thought it was spinning too fast for the 120VAC it was putting out. So, I bit the bullet and ordered up a brand new stator. I put it in and, well, the rpms are still about the same but, at least it's working flawlessly.
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Old 08-28-2019, 09:00 AM   #9
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Quote:
First off, NOT ALL the Onans with the magnets threw them off. I know several friends with them that have thousands of hours on them and not one has thrown a magnet.

Count me in that group. 12 years & 1900+ hours and the only problem has been a failed speed governor module.
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