Replacing DN50 alternator with smaller unit
 

Replacing DN50 alternator with smaller unit

Started by ChuckMC8, May 15, 2007, 05:38:20 PM

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ChuckMC8

May 15, 2007, 05:38:20 PM
My DN50 bit the dust and I replaced it with a 175 amp Motorola truck unit.
  I assumed that the correct way to wire it is to power the lug on the regulator. With the bus running during the alternator "test", I supplied 24 volts to the regulator lug and.......nothing happens.........
There is also an "R" terminal on the back (I thought to take a pic b4 I installed it, see below) with the regulator powered, I have 15 volts at the R terminal.....this is a fresh rebuild with a new regulator, so I assume that I have it wired incorrectly. Anyone know?

The New Alternator is also 24 volt........
Far better is it to dare mighty things,to win glorious triumphs,even though they may be checkered by failure, than to rank with those poor spirits who neither enjoy nor suffer much,because they live in the gray twilight that knows neither victory nor defeat.  Theodore Roosevelt (1858-1919)

Dallas

#1
May 15, 2007, 06:41:20 PM
Chuck,
I'm not sure about your alternator, but the Newer Motorola Alternators are built by Leece Neville now and are internally regulated.

That one looks like the Load Handler Series and from what I've read, it is one of the ones that has an internal regulator.

Dallas

NJT 5573

#2
May 15, 2007, 07:16:30 PM
Chuck, If you install a 12 volt alternator to a 24 volt system you will at least have a confused alternator! If you bought the best alternator for the bus it should be a "one wire" unit. It will be internally regulated and  just need a wire to go to the batteries that is large enough to carry the rated amperage. Do you have a 12 volt starter? Have you rewired the batteries to 12 volt?
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ChuckMC8

#3
May 15, 2007, 07:26:28 PM

(On equipment) When I have relaced old charging systems with Delco 12 volt self regulated alternators, some excite by revving the engine to a certain RPM and it would kick on. On diesel tractors that wouldnt rev up enough, I installed a momentary contact switch 12V to one of the spade terminals on thealternator and it would begin charging as soon as the momentary contact was made. I has assumed that the lug on the regulatior would need the moentary shot of 24v and it would excite the regulator and off she would go.

  I am pretty dense, but after 5 years of bus converting, including a complete conversion and mechhanical rebuild and repower, I just couldnt figure out that I would put a 12 volt alternator in to power a 24 volt system-
Far better is it to dare mighty things,to win glorious triumphs,even though they may be checkered by failure, than to rank with those poor spirits who neither enjoy nor suffer much,because they live in the gray twilight that knows neither victory nor defeat.  Theodore Roosevelt (1858-1919)

NewbeeMC9

#4
May 15, 2007, 08:51:38 PM
Could it be the one for the Tach?  That what myine is for i think.
It's all fun and games til someone gets hurt. ;)

Stan

#5
May 16, 2007, 05:11:04 AM
When a 24 volt alternator is generating, you should have one half of the output voltage at the "R" terminal. If you have 15 volts on the "R" terminal, it is generating and you should have 30 volts on the the main output. If you have 15 volts on the main output, that would indicate that one half of the bridge rectifier is open. If you have no voltage on the main terminal, I have no explanation other than the possibility that the rectifier is not connected to the bolt. This is unlikely since I expect all alternators are tested when rebuilt. Have you talked to the people who sold you the alternator?

pvcces

#6
May 16, 2007, 07:09:33 PM
ChuckMC8, if you have 15 volts at the R terminal, it sounds like the alternator is producing some power. How do you know that nothing happens when you furnish 24 volts to the regulator?

Tom Caffrey

Quote from: ChuckMC8 on May 15, 2007, 05:38:20 PM
My DN50 bit the dust and I replaced it with a 175 amp Motorola truck unit.
  I assumed that the correct way to wire it is to power the lug on the regulator. With the bus running during the alternator "test", I supplied 24 volts to the regulator lug and.......nothing happens.........
There is also an "R" terminal on the back (I thought to take a pic b4 I installed it, see below) with the regulator powered, I have 15 volts at the R terminal.....this is a fresh rebuild with a new regulator, so I assume that I have it wired incorrectly. Anyone know?

The New Alternator is also 24 volt........
Tom Caffrey PD4106-2576
Suncatcher
Ketchikan, Alaska

ChuckMC8

#7
May 17, 2007, 03:29:11 AM
 I am watching the volt meter when I apply power to the regulator. So, its not indicating more than 24.1 at  the positive lug on the alternator.
   I stopped at the local alternator-starter shop and the guy there says he will bench test it for me if I bring it in. So maybe I can do that today or tomorrow.
thanks for  the help.
  He did confirm that I have it wired correctly.
Far better is it to dare mighty things,to win glorious triumphs,even though they may be checkered by failure, than to rank with those poor spirits who neither enjoy nor suffer much,because they live in the gray twilight that knows neither victory nor defeat.  Theodore Roosevelt (1858-1919)

ChuckMC8

#8
May 17, 2007, 09:41:39 AM
I removed the alternator and took it to the shop for testing. The regulator is defective. I should have it back on and in business Monday. Thanks for the help- Chuck
Far better is it to dare mighty things,to win glorious triumphs,even though they may be checkered by failure, than to rank with those poor spirits who neither enjoy nor suffer much,because they live in the gray twilight that knows neither victory nor defeat.  Theodore Roosevelt (1858-1919)
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