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Onan 7.5 Quiet Diesel Shuts Down


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Old 03-26-2012, 10:38 AM
jc2 jc2 is offline
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Default Onan 7.5 Quiet Diesel Shuts Down

I'v got an Onan 7.5 Quiet Diesel, HDKAJ(H) with approx 550hrs in a recently purchased 2004 Dutch Star Class MH. We picked it up last week and run the gennie for about (4) hrs on friday with no problems. The next day we ran it for about (4) hrs again and this time it started surging and then shut off. The code appeared to be 3 blinks pause 3 blinks. I think the secondary cose was blink pause then 3 blinks or 13. This weekend I started it up and after running about 15 minutes, it shut down. Believe the code was 3 blinks pause 3 blinks again but the secondary code this time was 2 blinks pause 2 blinks or 22. Our previous rv gennies were gas so this one has me in the dark as to what's going on and why (2) different codes. Oil level is good, antifreeze good, fuel in main tank almot fuel. Any ideas guys?
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Old 03-26-2012, 01:15 PM
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EricWood EricWood is offline
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Default Re: 7.5 Onan Quiet Diesel Shuts Down

FC 13 = Inverter Undervoltage
FC 22 = Governor actuator overload

If your codes are correct, this could be a number of things. Definitely going to need service manual 981-0522 to troubleshoot yourself.

Can get a manual to you if you need it.


eric
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Old 03-26-2012, 08:35 PM
jc2 jc2 is offline
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Default Re: 7.5 Onan Quiet Diesel Shuts Down

I'm assuming this would be in pdf format. Would be appreciated if not to much trouble for you. Thanks
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Old 03-26-2012, 10:21 PM
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Default Re: Onan 7.5 Quiet Diesel Shuts Down

jc2,

Click on my name, and send me a private message (PM) with a good email and I'll get it to you. Yes, its in PDF format.

eric
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Old 03-27-2012, 10:27 PM
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Default Re: Onan 7.5 Quiet Diesel Shuts Down

fyi.....just sent the service manual to the OP. Now his fun begins!

eric
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Old 03-28-2012, 03:52 AM
lokay5 lokay5 is offline
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Default Re: Onan 7.5 Quiet Diesel Shuts Down

Now you know why they call it a "Quiet Diesel".
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Old 04-19-2012, 08:32 PM
jc2 jc2 is offline
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Default Re: Onan 7.5 Quiet Diesel Shuts Down

Finally got the unit checked at the dealer and it seems that some magnets came loose on the rotor(?) and will need to be replaced along with the stator. I love it when stuff happens and I'm clueless. Supposed to get it fixed next week when the stator comes in. This unit is in a 2004 dp and I've been reading bits and pieces about consistent problems in this time frame. Anything one can do to make these things more reliable or are they like the infamous Yugo auto many years ago?

---------- Post added at 07:32 PM ---------- Previous post was at 07:28 PM ----------

Finally got the unit checked at the dealer and it seems that some magnets came loose on the rotor(?) and will need to be replaced along with the stator. I love it when stuff happens and I'm clueless. Supposed to get it fixed next week when the stator comes in. This unit is in a 2004 dp and I've been reading bits and pieces about consistent problems in this time frame. Anything one can do to make these things more reliable or are they like the infamous Yugo auto many years ago?

Thanks for the manual Eric but my eyes started to cross as I read it.
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Old 04-20-2012, 10:09 AM
Magnetite Magnetite is offline
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Default Re: Onan 7.5 Quiet Diesel Shuts Down

Quote:
Originally Posted by jc2 View Post
some magnets came loose on the rotor(?) and will need to be replaced along with the stator.
This happened to me (magnets cam loose on my 6.5NHD) on the Permanent Magnet Generator. It caused a fire. I rewound part of the PMG stator and replaced broken up magnets. I started it up and it caused another fire - opening it up showed that the magnets I had not replaced had broken and come loose again. I ended up replacing all magnets but one and again partially rewound the stator.

My diagnosis was that the broken magnet bits hit the end of the PMG stator poles between stator and rotor, which drove the sharp edge of PMG laminations into the stator wires. Those wires are connected directly to the battery. The pole lamination pieces are connected to ground. The clearance between the magnets and stator laminations is only 1/16" or so. If anything gets in there and jams the magnet against the stator pole, it can cause the short and apply full battery voltage across a low resistance stator winding. I added a 15 Amp fuse in line to prevent this. It's run great since the last repair.
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Old 04-20-2012, 10:35 AM
rmchambers rmchambers is offline
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Default Re: Onan 7.5 Quiet Diesel Shuts Down

Sounds like if you have ANY of these magnets come loose it's time to replace them all. I've found a good source of these rare earth magnets but not sure if they'd be the right size/shape for what you guys are using them for though. They sure are fun to play with, hellishly strong.

http://s.dealextreme.com/search/magnets
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Old 04-20-2012, 11:58 AM
Magnetite Magnetite is offline
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Default Re: Onan 7.5 Quiet Diesel Shuts Down

Quote:
Originally Posted by rmchambers View Post
Sounds like if you have ANY of these magnets come loose it's time to replace them all. I've found a good source of these rare earth magnets but not sure if they'd be the right size/shape for what you guys are using them for though. They sure are fun to play with, hellishly strong.

http://s.dealextreme.com/search/magnets
I used scavenged computer hard drive magnets. I cut each in half and glued the halves together to get two thicker magnets = two poles per scavenged hard drive. The PMG has 18 poles, with each magnet piece including 3 poles (six magnet pieces).

If you reuse the original magnets, and there's no reason not to if they aren't broken up, you should insist that the back of the magnet and the inner surface of the rotor be very well cleaned before regluing. Typically there is a lot of rust on the inner surface of the rotor and the expansion of that rust is what eventually pushed the magnet loose.

I used E6000 adhesive on my magnets.

My second failure was not due to the reuse of original magnets. It was because during the first failure the magnets broke into many small magnetic pieces. One of them was magnetically stuck in a corner of the rotor and when I started it up, centrifugal force threw it off and between stator/rotor.

Make sure you clean out all the magnet bits before a restart.

---------- Post added at 11:40 AM ---------- Previous post was at 10:49 AM ----------

My comments relate only to my experience with my 6.5 NHD with the PMG (Permanent Magnet Generator) design. The PMG is widely used in the P-series engines. I looked at the 981-0522B manual which appears to cover the HDKAJ(H) and it has a PMA Permanent Magnet Alternator that isn't very similar, so I doubt my comments apply.

---------- Post added at 11:58 AM ---------- Previous post was at 11:40 AM ----------

The PMG is used to produce only battery charging power. It has a stator inside the magnets, and the magnets are inside a cast iron ring so that centrifugal force presses them out against the cast iron ring. You would think it would be hard for the adhesive bond to fail.

The PMA of the quiet diesel uses PMs glued to the outside of a rotor, and the stator is outside that. It appears that centrifugal force is trying to sling the magnets into the surrounding stator. That glue had better be really strong.

The PMA produces the full generator output, in a 3-phase stator. The stator 3-phase signal gets fed to an inverter which produces the final output AC voltage. I presume at low loads the engine can idle way down and decrease noise and fuel consumption. It's a fascinating design, but nothing like the simple rugged-as-a-brick Onans that most of us play with.
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