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Onan MDJE voltage drop


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  #1  
Old 09-26-2015, 05:20:27 AM
Restless Restless is offline
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Default Onan MDJE voltage drop

Onan mdje yd series
240 volt single phase
50 hz
1500 rpm
Same problem as 6 months ago. Volts have been steady 240 volts for the last 6 months but today volts went crazy 240 to 60 volts and every number in between and after about 20 minutes remained around 60 volts. Same as 6 months ago. Also the amps went from 0 to about16 amps with a load of 4 amps, could hear the engine load and unload as the amps jumped about .
Changed avr card with no change. Last time changed avr fixed the problem for 6 months. Any help would be appreciated. Regards Les.
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  #2  
Old 09-27-2015, 06:42:29 AM
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Billy J Shafer Billy J Shafer is offline
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Default Re: Onan mdje voltage drop

Sounds like you have a rotor coming apart. Wire rubbing shorting out.
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  #3  
Old 09-27-2015, 10:06:29 AM
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Default Re: Onan mdje voltage drop

Do you have a voltage adjustment remote from the AVR itself (ie on the control panel?)

Also, what about your other regulator you sent to Flight Systems 6 months ago, what'd they say?
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Old 10-02-2015, 04:16:58 PM
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Default Re: Onan mdje voltage drop

Sorry for the delay in answering,moving house. There is no remote voltage control only the one on the avr card.The report on the avr card that went to Flight systems for repair, stated they changed the a jumper lead and board tested ok.
Billy J Shafer, comment sounds as if the end is near.
Regards Les.

---------- Post added at 06:16 AM ---------- Previous post was at 06:12 AM ----------

Hi Billy, Thanks for your reply, if this is the problem, does that mean that the rotor has to be rewound? Regards Les.
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Old 10-02-2015, 07:00:40 PM
sdowney717 sdowney717 is offline
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Default Re: Onan mdje voltage drop

Take a hard look at the brush area, look at the slip rings etc...
Maybe watch it while running to look for arcing.
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Old 10-02-2015, 07:05:11 PM
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Default Re: Onan mdje voltage drop

Yd's don't have brushes. Maybe loose/corroded connections on the rotating diodes. Marine gens have a lot of issues with corrosion of the various coil windings , so Ohm out everything , look for signs of green corrosion on the individual wires. Cheers
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Old 10-02-2015, 07:22:07 PM
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Default Re: Onan mdje voltage drop

Quote:
Originally Posted by Restless View Post
Sorry for the delay in answering,moving house. There is no remote voltage control only the one on the avr card.The report on the avr card that went to Flight systems for repair, stated they changed the a jumper lead and board tested ok.
Billy J Shafer, comment sounds as if the end is near.
Regards Les.

---------- Post added at 06:16 AM ---------- Previous post was at 06:12 AM ----------

Hi Billy, Thanks for your reply, if this is the problem, does that mean that the rotor has to be rewound? Regards Les.
Yes you would have to rewind the rotor. Most of the time they fail completely.But I have seen them have what I call a rotating short. If you do send it to a rewind shop. Send rotor and stator so they can both be checked out.
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Old 10-02-2015, 08:09:29 PM
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Default Re: Onan mdje voltage drop

I'd start by :

1. Disconnecting the regulator from F1 and F2
2. Make sure the governor is keeping the engine running at 1500 rpm
3. Connect 12 VDC to F1 and F2 wires
4. Look at your AC output and see if it's still jumping around
5. If it is jumping around, you have a generator issue (could be the rotating diodes)
6. If not, it's probably the regulator
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Old 10-02-2015, 08:37:13 PM
sdowney717 sdowney717 is offline
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Default Re: Onan mdje voltage drop

http://www.wanderlodgeownersgroup.co...e%20Manual.pdf

Page 50 shows how to test these rotating rectifiers yourself using meters, exciter rotor and exciter stator and generator stator, is this appropriately generic enough for this gen?
I don't know, but if the owner can do it themself, I would look for a specific test procedure to try and figure it out..
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Old 10-02-2015, 09:18:16 PM
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Default Re: Onan mdje voltage drop

That is for a DKD but it is similar, I would go with Jims suggestion as the quickest way to get an answer. Cheers Dan
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Old 10-04-2015, 02:33:14 AM
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Default Re: Onan mdje voltage drop

I would like to thank everyone for their ideas and responses. I'm in the process of moving house and can't find time to get to the boat at the moment. When I can work on the boat, I'll will no doubt have more questions. Regards Les.
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Old 10-04-2015, 10:57:49 AM
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Default Re: Onan MDJE voltage drop

When you do get back on this project, try to locate this thread, and add to it, instead of starting another one...
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