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Technical older style Delco alternator confusion, 1 wire possible, or not?

Discussion in 'The Hokey Ass Message Board' started by toxonix, Jun 6, 2014.

  1. toxonix
    Joined: Jun 15, 2011
    Posts: 25

    toxonix
    Member

    I have a first gen Delco style alternator that i was hoping to run as a single wire setup, but I don't think it has an internal exciter. So I wired it up with the 3 wire setup: BAT terminal to battery+, Field #1 to the ignition acc/on switch to charge the field/exciter, Sensing #1 to the batter+. (battery+ are all on the starter solenoid's 12v+ side to keep things simple)
    I figured it was correct so started the motor to tune the carb, but when I went to shut it down, the damn thing kept running. The distributor was still getting 12v+ from somewhere in the circuit. So with my probe I found that Field #1 was supplying 12v back into the ignition circuit, not ground as I expected. WHAT? Neither one of those pins on the back of the alternator (not the power tap) should be supplying 12v, not the voltage sensor or the exciter input. The sensing circuit should be drawing voltage, so should the field, not supplying it. I'm basing my information on this:
    http://bob_skelly.home.comcast.net/~bob_skelly/alternator_conversion/wiring_alternator1.html
    Which shows the exact Delco alternator (older 3 wire style) that I think I have.
    Can I run this thing 1-wire without the Field#1 connection? Maybe I have the wrong alternator.
    I wanted to run it as a 1 wire setup, even fabbed a new bracket so it would fit on the 390FE block. :( This is not a 1-wire alternator with an internally switched exciter. Which is what I probably want.
     
  2. Put a diode in the wire between the ignition switch and alternator or possibly hook it to the accessory terminal. If you don't isolate the wire in some way, it will continue to feed the ignition circuit and the engine will keep running.
     
  3. toxonix
    Joined: Jun 15, 2011
    Posts: 25

    toxonix
    Member

    I'll give that a shot. That makes sense. What I'm seeing is the RMS voltage of the field feedback square wave. My probe just shows the RMS, not the rising/falling square wave.
    Thanks Rich!
     
  4. The old style orig Delco alternators are external voltage regulator (VR). Not sure how these can be made 1 wire. If the newer version with internal VR, you just need a self-exciting VR. Look on ebay or similar and you can buy them cheap. The new VR installation is pretty easy, hardest part is to hold back the brushes with a toothpick or similar. Otherwise simple mechanical.

    The reason your car kept running is exactly the feedback though the exciter wire. A diode cures the problem.
     
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  5. chopolds
    Joined: Oct 22, 2001
    Posts: 5,680

    chopolds
    Member
    from howell, nj
    1. Kustom Painters

    Yes, put a diode in the exciter circuit...but technically this is not a one wire alt. It is an internally regulated alt. A one wire has the magnetic exciter, and only one wire going out to the Battery. No filed wire.
     
  6. Is your Field wire run through an idiot light? Or direct to an ignition source? The Field is the ground for the idiot light. The light goes out when it has B+ on both sides of the bulb (when the alternator starts charging.) If it wired directly to the ignition, that's what's keeping the coil lit.
     
  7. Been using this system for 40 years. Early GM alt, Early(60s) Chrysler regulator. 12v bat power to alt as is normal. 12v hot from on side of ign sw to regulator. Wire from reg to Field on alt. Works great last a long time. Be prepared as this is not like GM intended. When you start the car it will charge 30 to 45 amps for about 15/20 seconds then go down until it feels Bat is good.
     
  8. twenty gallons
    Joined: Jun 7, 2010
    Posts: 444

    twenty gallons
    Member

    try putting your exciter wire #1 to the Acc side of the ign switch
     
  9. Im wiring my T at present and this has given me the info I need to wire the charging system. Thanks for all this useful info and tips. JW
     
  10. squirrel
    Joined: Sep 23, 2004
    Posts: 44,633

    squirrel
    Member

    The early (1962-1972) Delco alternators do not have a voltage regulator in them. The newer 3 wire 10-SI alternators (1973-up) have an internal regulator.

    you need a voltage regulator. Whether it's inside the alternator, or outside. I have the old external regulator type alternators on a couple of mine, they work great, because I have an external voltage regulator connected to them.

    You can't do what you seem to want to do.
     
  11. X2!
     
  12. In his original post toxonix provided a link about a 10SI to illustrate which alternator he was using. Figured he was just mistakenly describing it as "first generation" and replied as such.

    If you power the field on an early external regulated alternator it goes to full output, think he would have noticed that and maybe even smoked the alternator when he was tuning his carb.
     
  13. squirrel
    Joined: Sep 23, 2004
    Posts: 44,633

    squirrel
    Member

    maybe it's time for some pictures? First, the internal regulator, which CAN be converted to one wire:


    new.jpg


    And here's the old early style external that can NOT be converted to one wire.

    old.jpg
     
  14. tommy
    Joined: Mar 3, 2001
    Posts: 14,758

    tommy
    Member Emeritus

    Is it some kind of status symbol to be able to say I have a one wire alternator? I m certainly not an expert on one wire alternators but the only advantage that I can see is that it's easy to wire. Big deal!! It ain't rocket science. I've seen problems with one wires not excited enough to charge at low RPMs resulting in a dead battery from idling around on the fair grounds and never charging. I don't get the fascination with the one wire alternator bit then again I love generators. I grew up on them and I love my old memories.
     
  15. hoop98
    Joined: Jan 23, 2013
    Posts: 1,363

    hoop98
    Member
    from Texas

    Conversion regulator;

    [​IMG]
     
  16. squirrel
    Joined: Sep 23, 2004
    Posts: 44,633

    squirrel
    Member

    I use one of these instead....it looks so much more "1960s".

    reg.jpg
     
    hotrod54chevy likes this.
  17. Atwater Mike
    Joined: May 31, 2002
    Posts: 9,866

    Atwater Mike
    ALLIANCE MEMBER

    I have a 100 amp Police alternator on my SBC, converted it to 1 wire. Now, any time I start the engine, I have to rev it to 2800 RPM to excite the reg., then it charges 14.6 volts the entire time it's running.
    (before I converted it, the 14.6 volt charging was also prevalent. Thought it was the regulator, alt. is external grounded, engine to batt., then to chassis grounded with 6 volt braided flat cable!)
    Any ideas? (before I change back to 3 wire?) Hate that 2800 RPM excitement!
     
  18. The thing I don't like about the 1 wire setup is with no dash light (idiot light ! ?) is you don't know your V-belt has fallen off and is laying on the road behind you. No charging and no cooling, how many drive with one eye on the gauges all the time. Thing get hot real quick with no water circulating. Idiot light......I think not !!! JW
     
  19. squirrel
    Joined: Sep 23, 2004
    Posts: 44,633

    squirrel
    Member

    I like idiot lights....I guess I'm an idiot.
     
  20. mikhett
    Joined: Jan 22, 2005
    Posts: 1,403

    mikhett
    Member
    from jackson nj

    Which way does the diode go Anode to alt or cathode to alt?
     
  21. I believe the stripe goes to the ignition switch. JW
     
  22. hoop98
    Joined: Jan 23, 2013
    Posts: 1,363

    hoop98
    Member
    from Texas

    Cathode towards alternator.
     
  23. bchctybob
    Joined: Sep 18, 2011
    Posts: 1,955

    bchctybob
    ALLIANCE MEMBER

    My hot rod runs a generator so its no issue, but my Hemi powered vintage flatbottom has an alternator to keep the battery up for frequent starts. I wondered about the 1 wire vs three wire deal until I found madelectrical.com. They have great info on there to help you make a smart decision. They also sell diodes and adapter harness stuff.
    Basically, unless you really have a beef with the extra wires, the three wire system seems like the better way to go for most cars.
     

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