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DN50 replace
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I have not reached out to them yet, They might send theirs out to a specialist for evaluation and repair also. They are on the west coast, so that is good for me. I think there must be someone out there in this vast country of ours that works on bus and truck alternators and starters.
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Replacing the 50DN on an 8V92 can be done from the top through the engine access cover, or from the bottom using a lift to move the bus up and down as needed to be able to juggle the 50DN out and down the bell housing so it can be supported on someone’s shoulder and carried away.
If doing it from the top the entire coach interior has to be protected with plastic because there is going to be grease, grime and oil coming from it and it can do a lot of damage to carpets and fabrics.
I doubt it anyone who has no experience dealing with the gear driven 50DN on an 8V92 can do the job without a great deal of difficulty and a good chance of screwing something up. The Detroit Diesel manual needs to be followed exactly regarding re-installation.
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Thanks Jon, removal and installation, i can handle, looking for a someone that can look at it and test it is my quest currently. I have 4 possible scenarios in my head as to why i don’t have 12VDC out from this alternator. 1) The fiber coupler failed, alternator still good, just not spinning. 2) Fiber coupler failed due to alternator locking up, alternator not spinning. 3) Alternator failed due to some kind of massive load on it which broke the gear, alternator still spins. 4) the Gear is still installed, alternator spins normal, and Alternator is not producing power.
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It seems if you remove the mounting cradle it requires a special alignment tool to reinstall it. If anyone has a source for this tool please post it. Thanks, jeff
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Jeff, do you have a mechanically driven 50DN on the back of your engine?
Jeff and Lindsay
91 Marathon XL -
Mike, yes i do.
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All 8V92 engines had the gear driven alternator.
The Prevost manual for the coach years has an excellent section relating to the 50DN and testing it.
FWIW Prevost at the time did not provide much slack in the field wire and some alternator failures were only the field wire being pulled from its terminal. Try to look for the low hanging fruit first.
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I have some pics of the 8V92 top side (and alternator) looking down from the open hatch. I’ll try to find them and post.
Jeff and Lindsay
91 Marathon XL -
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“All 8V92 engines had the gear driven alternator.”
My 1988 Country Coach, which I purchased in 1999, did not have a gear driven Alternator. There were 2 belt driven alternators, one for 12V and another for 24V. I can’t say whether this was the original setup, a converters change or modified at some date in between.
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Thanks for posting that John. That may be a handy reference for those of us who are dealing with this. Jeff
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You’re welcome! I need to take photographs so I can remember (5 minutes later) what it looked like!
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Jon, you mentioned a manual with a lot of detail? do you or someone have a copy of that? My Bus docs were nil at best.
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John, Thank you for the pictures looks just like mine.
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Reminder, my 50DN is a 12 Volt version. I have Two 2/0 cables coming off the positive alternator post each one running to a 135 Amp Fuse, then onto the Battery Banks. One cable per pair of batteries.
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