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Thread: Delco 1-Wire Alternator Questions

  1. #1
    Join Date
    Nov 2006
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    California City, CA USA
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    432

    Default Delco 1-Wire Alternator Questions

    I have a D7 17A with a Delco Alternator. It is direct driven by the Generator gear (via a coupling (Its name escapes me now)). There isn't a label of any kind left on it. It has four terminals: Batt, R, (under plastic cover on top) 1, and 2. This is a 24V system (apparently the voltage regulator has been changed).

    Does anyone know what the model number might be?

    If I jump Batt and R it briefly charges (per ampmeter) and then quits. Do I have to do something with the 1 or 2 terminals (with a switch, etc.) to get it to charge?

    100_0492.jpg100_0493.jpg100_0494.jpg100_0495.jpg

    Thanks. Daron

  2. #2
    Join Date
    Jul 2016
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    Lancaster CA
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    Default

    It is a delco 10si 30 amp or 12si 70 amp. Self exciting. ( internal volt regulator) Only uses 1 wire. Sometimes takes considerable rpm to make it excite. Are the batteries low? Batt to R may make it think the batteries need a charge. Soon as it charges reg senses that batteries are up. On hot rods they run a wire from batt to terminal 2 to improve sensing. Early si alternators were wired with terminal 2 going to battery on the ignition switch where voltages are slightly less than right at the batt terminal. Give me a call if you need more help. John
    Cat 12 grader, 8T running and restoring, Cat 12 grader 9K3585. parts machine, Adams leaning wheel Pull grader Mod # 28,

  3. #3
    Join Date
    Mar 2017
    Location
    Oklahoma
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    if the alternator is still 12 volt there should be a parallel switch somewhere to charge the 24 volt. are you sure the starter is not 12 volt? i "correct myself" the 10si is a 24 volt alternator. i didn't know they made a 24 volt single wire alternator. i would confirm the alternator is indeed a 10si and move from there. sorry for the confusion.
    Last edited by captainhowdy; 10-18-2017 at 08:15 AM.

  4. #4
    Join Date
    Apr 2013
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    125

    Default

    Most auto parts stores will test for free.

  5. #5
    Join Date
    Jun 2007
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    Colorado West
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    Default

    The worst thing about 1-wire alternators in slow-revving applications is that you have to wind it up to make it kick in & start charging. Not the best thing for a cold engine...
    The second worst thing is that they sense voltage right at the alternator, which is the worst place to do that...a 3-wire senses voltage at the switch, which accounts for voltage drop between the alt & the load. A 1-wire will never keep the batteries at full charge.
    Yeah, I know they are easy to hook up & cheap...
    If it's a rebuilt, there is probably no numbers on it to go by.

  6. #6
    Join Date
    Nov 2006
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    Corralitos, Ca.
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    Default

    As mentioned that is a 24v Delco 10SI alternator conversion with Motorola to Delco mounting flange housing.
    It is a single wire conversion with low cut in rpm internal regulator. Ignore the original terminal designations as they are for the original 3-wire application. The "R" terminal is for a electric tachometer that would only read correctly for specific rpm installations. Complete replacements are available (about $110) or individual parts can be had although the average auto parts store may not have the 24v low cut in regulator. Coupling is a "Lovejoy"

  7. #7
    Join Date
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    Default

    To test the regulator, and brushes etc, rev it up and then use a small screwdriver etc to short the regulator tab to the housing. It is located in a D shaped hole in the rear of the housing. If regulator is faulty the voltage will immediately rise (to higher than normal if the batteries are fully charged). If there is some other problem with it, shorting the regulator to full field it will have no effect on the voltage.

    They aren't too hard to disassemble and replace brushes, regulator etc. Easiest thing is to take it to a shop that works on starters and generators etc. It should be an easy fix for that kind of shop. If you want a new one you can find a 10SI 24 volt Negative ground with the standard housing online at places like Rare Electrical etc. You would have to swap the main housing to the Motorola type. Just have to pin the brushes back in the holder before reassembly and pull the pin once it's back together.
    D2-5J's, D6-9U's, D318 and D333 power units, 12E-99E grader, 922B & 944A wheel loaders, D330C generator set, DW20 water tanker and a bunch of Jersey cows to take care of in my spare time

  8. #8
    Join Date
    Jul 2016
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    Lancaster CA
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    All good advise except take it to a shop. Spent 3 years in an auto electric shop the specialized in heavy duty stuff. Can take it apart in my sleep. Is it still at Arlies or at home? Give me a call.
    Cat 12 grader, 8T running and restoring, Cat 12 grader 9K3585. parts machine, Adams leaning wheel Pull grader Mod # 28,

  9. #9
    Join Date
    Nov 2006
    Location
    California City, CA USA
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    Default Thanks All...

    ...for all of the suggestions. I think my problem is the regulator and low RPMs. I probably won't have time to do much with it for the next several days (the tractor returned home last SUN though). I think I'll jump the #2 terminal to the BAT terminal and see what happens as I see those two connected in some 10si wiring diagrams. I think I did that to an inoperative charging system on an old Owatonna (sp?) loader about a year ago (I wired it to the ignition switch).

    Thanks again, Daron

    P.S. Lovejoy- That's it!

  10. #10
    Join Date
    Jul 2016
    Location
    Lancaster CA
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    Default

    Try running a temporary wire from 2 back to the ing. (away from main output)
    Cat 12 grader, 8T running and restoring, Cat 12 grader 9K3585. parts machine, Adams leaning wheel Pull grader Mod # 28,

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