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Author Topic: Replacement 24V Alternator for MC5...8V71  (Read 6252 times)
NCbob
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« on: August 23, 2007, 11:11:42 AM »

I have searched the archives and most of the topics hit all around my search and none directly at it.
So here goes.....

It appears that my original engine (24v) alternator system has said goodbye.  Why am I not surprised?
It's only 39 years old...and the voltage regulator bolts rusted off at the mounting bracket so it's just sitting in that box and subject to all sorts of jolting.

It doesn't make much sense to me to do anything with this old system (the OTR A/C is long gone and the heat will soon be) and whatever parts I'd need are probably too expensive and unobtainable. So, I asked myself, "Myself, why don't we just replace the existing alternator with a late model alternator with an internal regulator?"  And I answered, "Hmm, perhaps the guys on the Board have done this so beating my head up against the wall doesn't make much sense....and it sure feels good when I stop!"

So fellas, that's my question..Is there a replacement 150-200 amp alternator out there for an 8V71 which will mount up in the same place as the old one without a lot of modifications and fuss and give me what I need to maintain the 24V Starting batteries and keep the 12V house batteries peaked up through the Vanner charge divider? That should be sooo simple for you more experienced techie's than me....please?

I'm not asking it to keep up with a lot of load...just occasionally running lights (on those rare occasions I get stuck driving in reduced visibility) or in the case of the 12V system...a small inverter to keep the fridge running and the headlights.

NCbob
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« Reply #1 on: August 23, 2007, 11:55:08 AM »

I doubt that you will find an alternator as good as the original 50DN. If the regulator is hanging on the wires you need to do some troubleshooting to determine if there is anything wrong with the alternator or the regulator or if you just have a wire problem.  Both the alternator and regulator are in common use and repairs are readily available.

It is not easy working in a MC-5 bay on the alternator and would be quite a job building a new bracket for a different alternator.

The common setup with a 24 volt 50DN is to run a 24 volt house battery and charge it with the 50DN and then use the Vanner Equalizer to provide the 12 volts needed for the house.
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NCbob
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« Reply #2 on: August 23, 2007, 01:20:17 PM »

Thanks for the comeback, Stan...I have determined that there is NO output to the batteries.  Now, too it could be one of the field relays in the driver's panel..just haven't gotten that far yet.

And yes, you're right. working around that regulator in a 5 is a PITA. The inside box would have to come off before I could get to the regulator mounting brackets and it looks like at least an all day job just to remount the regulator before I can see if there's any alternator output.  Not a job I want to tackle in August heat...but will snipe at it a little every morning.

There's certainly no one here in 'Podunk' who could repair the alternator should it prove that's the problem.
I'll just nibble away at all these little things and hope I can be ready for Kyle's Non-Rally in October.

NCbob
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« Reply #3 on: August 23, 2007, 02:15:29 PM »

Bob- the Delco 50DN is probably one of the best alternators ever made.  Being gear driven, pressure oil lubed, cooled with the oil, completely sealed, and no brushes, are very long lived-just look at the one you have now after 39 years!  I replaced my 50DN last year.  I have an advantage in that mine is a V drive and can get to the rear of the engine relatively easy.  The 50DN does weigh in at a heafty 100lbs.  I also installed a new digital regulator that regulates closer, but can still see the headlights go bright and dim a bit.  The digital regulator is about the size of a deck of cards and does have a voltage adjustment on it.  I have my regulator installed inside the bus to eliminate heat and dust.
I believe Leece-Neville made a direct drive alternator in the 150amp range that is more the size of a truck alternator.  Other than that, you'd have to install a pulley in place of the 50DN alternator to be able to run any of numerous belt driven alternators available.  A truck size alternator can be bought for about $250.00 new with internal regulator.  As compared-my rebuilt 50DN exchange with new regulator was about $1,900.00.  Just remember though-39 years of service is alot of time-compared to having to crawl up to adjust the belt periodically.  Good Luck, TomC
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NCbob
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« Reply #4 on: August 23, 2007, 05:04:28 PM »

The more I look at this, and more testing will come tomorrow morning, it might just be the regulator. I found the number on the Delco site but am having the devil's own luck in finding a parts house that might have a replacement.  And the beat goes on.......

Bob
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Gary '79 5C
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« Reply #5 on: August 23, 2007, 05:09:13 PM »

NcBob,
Good luck with the regulator, without the field voltage no output from the alternator.
TomC, you did great with a rebuilt unit for $1,900, The alternator was my first failure on my 5C, and the only replacement I could locate was NIB from MCI, @ $2,800 W/O tax. I thought flying maint. was high. I did find a used unit and replaced the shaft I needed for a lot less.

Gary
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« Reply #6 on: August 23, 2007, 05:12:38 PM »

Bob I have pulled and replaced the belt drive 50DN in my 5C and it is a bear. To modify that area and re injuner a different alt would be doable, but not easy. If your over the road air is gone you should have a spare space on your injun pully. It would be a lot less difficult to design and build a new setup back there someplace. I've seen that done lots of times. I'm sure many people would be happy to send you a photo of thier setup.
 I would diagnose the 50DN first!
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« Reply #7 on: August 23, 2007, 05:27:44 PM »

Jim, that's exactly what I plan to do in the morning.  The alternator should have enough residual magnetism to kick it off and I might be able to read a small voltage at the R terminal of the regulator to ground.  If I see anything (I use a Fluke digital meter) I'll feel better about the alternator.

Too, if I do find a voltage I should be able to excite the alternator (doesn't that sound exciting for an old man?) by putting even a small amount of voltage to the field wire. Normally it would take 24VDC to 'full field' it but it would prove to me that the field relays, both of them, are operating properly and the alternator is OK.

Ah, the pains we go through too keep these old girls working and looking their best! Huh

Thanks for the reply.....

Bob
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« Reply #8 on: August 23, 2007, 05:49:58 PM »

Bob: If your alternator is original, it should be a belt driven (4 belts) and air cooled which makes it easier to take out but in a 5 it is still a bear.

IIRC a 50DN puts out max voltage with about 10 volts on the field winding. If you disconnect the field wire (in case of shorted regulator) and hook your volt meter to the battery terminal it should show the battery voltage. Now start the engine and put a jumper wire between the battery terminal and the field terminal. If the voltage jumps up, the alternator is likely good.
 
If the alternator charges with full voltage applied to the field, temporarily connect the regulators three wires (battery, field, ground) to the alternator and try the engine again and see if the battery voltage rises. If that is OK then you are down to checking the wires and relays between the alternator and the regulator compartment.
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« Reply #9 on: August 23, 2007, 06:08:20 PM »

Hello Bob:

    If you need someone to repair your alternator and possibly get you a voltage regulator.  You need to talk to Phillip Hulsey at Star Auto Electric
in Cornelia, Ga.  telephone # 706-778-5656.  He is able to check yours and
tell you what's wrong with it and give you a close price.  I've seen him repair
big truck starters, down to motorcycle starters.  He can do it all, and a heck
of a nice guy.  If you need directions give me a call 706-778-five/zero/six/three.  Good luck.
                                             Glen Rice   
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NewbeeMC9
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« Reply #10 on: August 23, 2007, 07:39:22 PM »

Hey Bob,

I had a Guy in Greenville, not far off 385 in mauldin, rebuild/rewind my 50DN for about $800, if you take your regulater to him he can check/set it.  Mine alt is belt drive.  All the other alt shops in town said go to him.


also heres another thought

go bac where the AC was like the others said and use one of these

http://cgi.ebay.com/ebaymotors/Delco-Remy-24-Volt-Alternator-One-Wire-105-AMP_W0QQcmdZViewItemQQcategoryZ33573QQihZ018QQitemZ280143704102QQrdZ1QQsspagenameZWDVW

and get another one wire 12 v one for the 12 volt system.  find some nice chrome alt brackets from the hot rod section.  i believe you can hook the 24 v in there by the starter.

also maybe for the house batteries,  remember this thread

http://www.busconversions.com/bbs/index.php?topic=3160.0

and this? http://amplepower.com/products/genie

also from the truck places you can get a 175 amp alts alot cheaper,  if yours is like mine you may not have to fab too much,  the turnbuckle is adustable.

a lot is what i remember from the old board  maybe some other, brighter ones will chime in

HTH
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belfert
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« Reply #11 on: August 23, 2007, 08:56:19 PM »

Be very careful if you remove the DN50, especially by yourself.  It is very heavy.  I removed mine by myself, but I'm only 35 years old.  I'm planning to have help to put it back in as getting it back in will be more difficult.

I wouldn't want to see someone getting hurt working on a bus.
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NewbeeMC9
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« Reply #12 on: August 23, 2007, 09:36:20 PM »

Be very careful if you remove the DN50, especially by yourself.  It is very heavy.  I removed mine by myself, but I'm only 35 years old.  I'm planning to have help to put it back in as getting it back in will be more difficult.

I wouldn't want to see someone getting hurt working on a bus.

He's right about that, I took mine out and replaced it by myself.  wouldn't reccomend to anyone

the nine has a hatch in the floor right above it too.
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niles500
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« Reply #13 on: August 23, 2007, 10:05:11 PM »

NCBob - you are just close enough to contact Gene Rochester in Walhalla SC - HE knows more about alternators than ANY human being on earth - unfortunately he's not a busnut anymore - old phone numbers are (don't know if they're any good now) 864 882 3636 & 864 888 8578 - HTH
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NCbob
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« Reply #14 on: August 24, 2007, 04:36:41 AM »

Many thanks to all of you for your advice and information. This situation isn't really over my head, so to speak, but it reminds me of when I was a kid....having measles was a terrible inconvenience but knowing that the neighbors' kids had been there or were there sure made the suffering less intense. Huh

I will attack the problems with renewed vigor this morning....thanks again to all.

Bob
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