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Old 04-05-2018, 20:42   #1
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Replacing very old alternator

Hi,

We have replaced a very old start alternator (Valeo brand) with a shiny new Delco ( Delco 65 Amp Standard Alternator ). This is for our Perkins 4108 (1988 or so vintage).

In addition to positive, ground and Tach - there were some wires coming from the old alternator that I do not understand and are not sure if or where to reconnect. Fortunately they are labelled:

1.Reg field
2.Diode trio
3.Charging light

Here is a picture of the old alternator:
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Old 04-05-2018, 21:01   #2
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Re: Replacing very old alternator

it sounds like your old alt was external regulatored. the new one won't be.

you'll either have to remove the old ext regeraltor and figure our it's wiring. or remove the new alt and have it modified for ext reg.

charging light would go to the dash warning light.
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Old 04-05-2018, 21:20   #3
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Re: Replacing very old alternator

Ok. I will check the wiring. Shouldn't be too hard to figure out now that I understand somewhere in the electronics bay I should expect to find a external regulator.

I have seen the Balmar one but not one that looks like its got anything to do with that old Valeo.

Cheers

AG
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Old 04-05-2018, 22:00   #4
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Re: Replacing very old alternator

If you were going to trace the wires to find the old regulator - which one do you follow? reg?
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Old 04-05-2018, 22:11   #5
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Re: Replacing very old alternator

Either the red or orange marked diode trio. One will go to VR one to lamp.
Not convinced its externally regulated but if it is, that is where they would go.

https://alternatorparts.com/img/alte...%20diagram.jpg

That is a 10si clone. I have wired one of those in with its internal reg. (10si, 120A)
Too much down rating, so I open circuited the IR and hooked it to a smart external reg.
Then it overheated in a matter of minutes. I ditched it for a Bosch.
Doesn't heat at all and kicks off at 100A.
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Old 04-05-2018, 22:13   #6
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Re: Replacing very old alternator

The field wire is the one that tells the alternator how much power to output, so yes, it should run from the regulator to the field terminal of the alternator. The regulator controls the current on the field wire (typically from 0 to 6A) which in turn controls the magnetic field strength in the alternator and thus the output.

The Delco you linked has an "excitation" connection, this is a little nebulous in definition, it could be the field from external regulation or it could simply be a switched wire from the ignition system to tell the internal regulator to run. Couldn't find anything in their short description about type of regulation on the new one.
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Old 04-05-2018, 22:17   #7
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Re: Replacing very old alternator

Quote:
Originally Posted by Dsanduril View Post
The field wire is the one that tells the alternator how much power to output, so yes, it should run from the regulator to the field terminal of the alternator. The regulator controls the current on the field wire (typically from 0 to 6A) which in turn controls the magnetic field strength in the alternator and thus the output.

The Delco you linked has an "excitation" connection, this is a little nebulous in definition, it could be the field from external regulation or it could simply be a switched wire from the ignition system to tell the internal regulator to run. Couldn't find anything in their short description about type of regulation on the new one.
Thanks. I should be able to find the old regulator (if there is a external one) from that.

In terms of the new regulator - if I ignore the old wires it seems straight forward:

1. Connect + and Ground.
2. Connect wire to tach gauge
3. Connection wire to ignition

Cheers

Al
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Old 05-05-2018, 12:17   #8
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Re: Replacing very old alternator

Al-
There should also be a "Voltage Sense" lead. That goes from the regulator, or from an integral alternator, directly to the positive battery terminal, in order to let the system know how much loss there is in the wiring and what the real battery voltage is. On some boats it is tied back into the alternator output to simplify wiring, but that's a kludge.
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Old 15-05-2018, 03:22   #9
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Re: Replacing very old alternator

Update: I found that there is a external regulator for the starter alternator.

The new alternator has a internal one - so I guess the external regulator from the old alternator is no longer needed.
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Old 15-05-2018, 08:29   #10
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Re: Replacing very old alternator

An external regulator MAY be smarter and more robust than the internal (integral) one. Check into the options and ratings for both. If nothing else, the external one can dissipate more heat. If you decide the external one has reason to be kept, any alternator shop can pull out the correct leads for you. Sometimes even add an "internal/external" switch, so that you can run on the external, and have the internal as a hot spare in case the external quits.
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Old 02-06-2018, 18:02   #11
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Re: Replacing very old alternator

A wee update to the new alternator thread for anyone who may have a similar problem in future.

INITAL PROBLEM:

Tacho needle was bouncing all over the place. Tach is connected to factory alternator on a Perkins 4.108. The original alternator was a Valeo of some sort with a external regulator. The alternator was only used for starting as we have a Balmar for house.

The bouncing was more pronounced when in float. I checked this by making the motor turn over without starting it to drain battery then starting it and the bouncing would go away until it hit float.

SOLUTION:

Went to the helpful people at Trans Atlantic Diesels who sold us a new Delco alternator. Had to change the mounting bracket but other than that it plugged right it. Now our alternator needle is rock steady. In addition the Delco uses a internal regulator so we got rid of some extra wiring we didn't need to.
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Old 02-06-2018, 18:31   #12
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Re: Replacing very old alternator

That's to bad because you can't charge a large batt bank with an internal reg.
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Old 02-06-2018, 21:35   #13
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Re: Replacing very old alternator

Quote:
Originally Posted by Ecos View Post
That's to bad because you can't charge a large batt bank with an internal reg.
What do you mean too bad? I don't need to charge a large bank. I am only charging the starter battery. We have Balmar for house bank.
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Old 03-06-2018, 10:07   #14
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Re: Replacing very old alternator

Quote:
Originally Posted by Ecos View Post
That's to bad because you can't charge a large batt bank with an internal reg.

That appears to be incorrect.


Here's why:


How Alternators & Regulators Work PLUS External vs. Internal Regulators (by Maine Sail): http://forums.sbo.sailboatowners.com...d.php?t=125392
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Old 03-06-2018, 10:12   #15
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Re: Replacing very old alternator

Maybe with tolerant FLA banks, or where the alt is just contributing early charge stages at high amps.

If you want precise staged charging from alternator output alone, I believe none of the stock internal regs are as adjustable as the best external ones.
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