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Technical Alternator wiring issues

Discussion in 'The Hokey Ass Message Board' started by Grandpacharli, Aug 17, 2021.

  1. Grandpacharli
    Joined: Feb 17, 2020
    Posts: 27

    Grandpacharli

    Hi so I’m having issues with my 63 c10. The alternator will not kick in and as a result I had a flat battery the other day after a nighttime drive.

    I have bought a new 3 wire gm si series alternator. I’ve wired it correctly the same as my old one which ran for years like it . Pin 1 is to exciter pin 2 12v bat and then that goes to the power output on the back with a bat cable that goes to the starter.

    if I remove the bat cable whilst running the engine the generator emits power but when I put it back on to supply the truck it dips off as if its straining under load but I believe still running as it should. But I only see 12v at the battery.

    did some digging and the exciter wire when ignition is off is constant 12v live and it’s travelling down that wire from the alternator to the fuse board and into the accessory loom so powering my radio etc with ignition off ?! If I unplug the exciter wire under dash radio goes out and then will work as it should when you turn on ignition.

    So my question is should I have 12 v coming from the exciter on the alternator when it’s not running ? I don’t think that’s right and why would it happen? And I also read that the exciter needs over 12v to excite the alternator is that true ?
     
  2. brading
    Joined: Sep 9, 2019
    Posts: 475

    brading
    Member

    Is this how you have got t wired up. You should have no voltage coming out of terminal 1 when it is not running.
     

    Attached Files:

  3. Grandpacharli
    Joined: Feb 17, 2020
    Posts: 27

    Grandpacharli

    Yes that’s excaxtly how I have it . I just don’t get it unless somthing is arching on the plug I have no idea. It does it on my old alternator and new. And that’s with engine off key off. If I disconnect it under dash I get live from the fuse board with ignition on engine off and live from alternator. Switch ignition off and alternator wire stays live and so powers all my accessories it’s mad. It’s a new loom etc also American auto wire one.
     
  4. I believe wire #1 should go to the battery so it reads the condition of the battery, not connected to the output wire as that makes it a 2 wire alternator. JW
     

  5. Aside from wiring schematic, I ran across this once. Some rebuilders leave a pin in the case to hold the brushes up, while re-assembling. Check and make sure it's still not there.I don't have a picture, but should be able to find location for the hole, online. I've use a toothpick to assist me in the past. It's removable, after assembly.
     
  6. In the diagram above, the green wire should come from the "gen" light or an "ignition" source.

    I'm not sure that attaching the "bat" terminal wire from the alternator to the starter will be an issue. But to be sure, I have mine attached to the battery.
     
    26 T Ford RPU likes this.
  7. Sporty45
    Joined: Jun 1, 2015
    Posts: 1,021

    Sporty45
    Member
    from NH Boonies

    That exciter wire should be a switched ignition wire. You could have a problem in your fuse board. Are you running a charge indicator light? Does it function properly?
     
  8. Sporty45
    Joined: Jun 1, 2015
    Posts: 1,021

    Sporty45
    Member
    from NH Boonies

    I have a Painless wire kit, so not sure if wire numbers would be the same, but it should give you the general idea. The 914 wire is the exciter wire.
    From my instructions:

    CHARGE INDICATOR LIGHT Those wanting to add a charge indicator light will need to re-route the WHITE #914 wire found in the Alternator Section of wires. This wire will be connected to the light and then out the other side of the light to the alternator voltage regulator. The way the light will function is this: Electrical current moving from the fuse block, through the filament, and out to the alternator causes the light to illuminate. This light illuminates when the key is in the ON/RUN position and the alternator is not charging because the engine is not running or when the alternator is not working properly. Once the alternator is charging, the voltage regulator no longer needs the switched ignition voltage supplied by the #914 wire, which stops the current flow. Since power is no longer flowing through the filament, the bulb does not illuminate.
     
  9. Grandpacharli
    Joined: Feb 17, 2020
    Posts: 27

    Grandpacharli

    I had it wired as above before and it worked fine. Something in the wiring is wrong I believe but that was how it was before when it worked.
     
  10. Grandpacharli
    Joined: Feb 17, 2020
    Posts: 27

    Grandpacharli

    I know the hole your talking about but it does kick in and work IF I pull the bat feed on the alternator off and you can hear the change in alternator noise when you do . But when you put the bat cable back to the stud on the alternator it dips off. I don’t think the alternator dies off I think it’s loading off somewhere I’m just not sure where
     
  11. Grandpacharli
    Joined: Feb 17, 2020
    Posts: 27

    Grandpacharli

    The problem seems to be the alternator. The accessory loom only gets power when ignition is off from the exciter wire on the alternator . I just can’t understand why it’s constantly live.
     
    Sporty45 likes this.
  12. All this drama can be fixed with a 1 wire alternator!

    Ben
     
    Flathead Dave and hemihotrod66 like this.
  13. 51504bat
    Joined: May 22, 2010
    Posts: 3,168

    51504bat
    ALLIANCE MEMBER

    And for those who say a one wire won't initially charge at idle, my flathead has a one wire and immediately charges as soon as it fires up. Just my experience.
     
    Flathead Dave and firstinsteele like this.
  14. jaracer
    Joined: Oct 4, 2008
    Posts: 1,314

    jaracer
    Member

    Your wiring may be correct if it is wired as per your picture. Before going too far, you need to test the alternator. With all the wires connected, you need to use a small screw driver to ground the terminal inside the D shaped hole. You just touch the terminal and the alternator case. If the alternator starts charging, the internal regulator is bad. If it doesn't and you have it wire per your diagram, there is something internally wrong with the alternator. Delco 10SI full fielding instrucitons.jpg
     
  15. MeanGene427
    Joined: Dec 15, 2010
    Posts: 1,963

    MeanGene427
    Member
    from Napa

    Tractor Supply sells 1-wire alts that charge at idle, I have two, on my Ford 8N and 850 tractors- they work perfectly
     
    Flathead Dave likes this.
  16. Grandpacharli
    Joined: Feb 17, 2020
    Posts: 27

    Grandpacharli

    So I’m back home now working on it . And the power from the batter at terminal 2 is getting to the exciter wire by link between the two spade terminals on the alternator ? Is this right ? Can’t be surely.
     

    Attached Files:

  17. justold
    Joined: Jan 28, 2013
    Posts: 15

    justold
    Member

    The lamp wire needs a #57 lamp in the circuit or a diode . That terminal will back feed . You should NEVER operate an alternator open circuit !! You may have toasted the output diodes .
     
    firstinsteele likes this.
  18. Grandpacharli
    Joined: Feb 17, 2020
    Posts: 27

    Grandpacharli

    Okay , so I’m getting some where now !
    I’ve hooked u the main power to the stud as before and then from there the power supply to terminal 2 . And removed terminal 1. The alternator now fires up with power. 16 volts I’m getting IF I unhook the power from the back of the alternator stud as soon as I reconnect it struggles and the charge isn’t great enough to charge the bat so I’m guessing it’s shorting out !? No burn smells though
     
  19. brading
    Joined: Sep 9, 2019
    Posts: 475

    brading
    Member

    Sounds like something is wrong with your wiring.
    (1) The green wire should go from I terminal ( ignition terminal ) on the ignition switch to the number 1 terminal on the alternator sometimes via a charge warning light. It sounds to me that the green wire at the moment goes to the A terminal ( accessories terminal ) on the ignition switch which is why you are getting accessories on with the ignition off.
    (2) Sound to me like you have a faulty regulator in your alternator as there should be no feed out of terminal 1 when the engine is not running. This is how it should work. There is no power coming out of terminal 1. You turn the ignition on and this feeds 12v to terminal 1 on the alternator lets say via the warning light ( makes it clearer to understand ) this goes to earth in the regulator so your warning light comes . You start the engine the alternator build up power then basically turns the earth off and sends 12v via terminal 1 to the green wire. Now you have 12v coming from the ignition switch and 12 v coming from terminal 1 alternator. Now you have 2 opposing 12v volts which cancel each other out so that you have no voltage in the green wire, no power to the charge light and it goes out.
    If it would help I can PM you some diagrams.
     
  20. Mr48chev
    Joined: Dec 28, 2007
    Posts: 30,191

    Mr48chev
    Member

    I have every Delco alternator swap wiring conversion diagram that I find saved here. Photobucket
    This guy down in El Paso sells a slick plug and play put a diode in the line kit that while a bit bulky looking under the hood of a hot rod works real well as I bought one a while back rather than chase all over looking for a farm equipment dealer that had the diode I needed.
    CHEVY DELCO ALTERNATOR HARNESS ANTI- FEEDBACK DIODE 10SI 12SI 15SI 27SI WIRE | eBay
    If you don't have a diode or idiot light in the line it drains your battery.

    One thing I have never subscribed to the hillbilly method of checking an alternator by disconnecting the battery while the engine was running. I know Chrysler removed the battery from a Valiant or Dart and drove the thing several hundred miles in the late 50's to show that the alternator worked great and half the shade tree mechanics in the country decided then and there and it has been passed down as to that is how you check one but it is a shade fucking tree way of doing things and not the right damned way to do it even if you live so far back in the hills you only get mail once a week. Learn how to correctly test things.
     
    Last edited: Aug 17, 2021
  21. harpo1313
    Joined: Jan 4, 2008
    Posts: 2,337

    harpo1313
    Member
    from wareham,ma

    If they are tied togeather , theres your problem.I would return it.
     
    26 T Ford RPU likes this.
  22. Johnny Gee
    Joined: Dec 3, 2009
    Posts: 9,574

    Johnny Gee
    Member
    from Downey, Ca

    No, there should not be any 12v + out put. Something's up with the alternator.
     
  23. Alternators are crap these days. It took me 4 to get a working one when I needed a new one.
     
  24. Grandpacharli
    Joined: Feb 17, 2020
    Posts: 27

    Grandpacharli

    Terminal 1 is connected to the excited wire one the American auto wire kit. It plugs in under the dash. And that then goes to the same feeds in the accessory’s loom . The problem isn’t that though it’s the cross link on the alternator on the picture in the last post. It joins 1 and 2 together which gives that look a permanent feed. Which I’ve never seen before!

    I understand how the light works. It basically won’t let the bulb have an earth so long as the current Is equal both sides otherwise the light will be dim or even bright when off.

    The alternator now comes on with out the exciter wire hooked up and runs strong but as soon as I hook the power lead to the back of the alternator it seems to die off. That’s the next problem.
     
  25. Grandpacharli
    Joined: Feb 17, 2020
    Posts: 27

    Grandpacharli

    I live in he Uk . I bought it off a guy over here who’s had it for a year or so . Do you think cutting that link that connects the two would Benifit in anyway ?
    I’m now getting power from the alternator but as soon as I hook it up the alternator shuts off so can’t get the battery to charge.
     
  26. harpo1313
    Joined: Jan 4, 2008
    Posts: 2,337

    harpo1313
    Member
    from wareham,ma

    Never seen the link , but will go out and look at one.
     
  27. Shorty
    Joined: Sep 11, 2002
    Posts: 46

    Shorty
    Member

    Did you or have you tested the new alternator? Maybe it's defective, I'm just asking.
     
  28. Grandpacharli
    Joined: Feb 17, 2020
    Posts: 27

    Grandpacharli

    I think it’s wiring related because 3 alternators all do the same thing. It’s as soon as you hook it up to power the alternator dips off or the alternator stops charging altogether, I’m just lost with it . Still haven’t figured it out.
    I’ve wired an idiot light up for it and it goes right out to say the alternator is charging yet I only see 12 at the battery.
     
  29. Mr48chev
    Joined: Dec 28, 2007
    Posts: 30,191

    Mr48chev
    Member

    You are pissing into the wind and expecting to not get wet if you don't take the alternator to an auto electric shop to have it tested. Sorry to have to be blunt but if you do not do things step by step correctly you will not get it sorted out.

    I've done several this way and never had an issue. The diode is available at Ferguson tractor dealers.
    [​IMG]
     
  30. Wrench97
    Joined: Jan 29, 2020
    Posts: 505

    Wrench97

    Sounds like a defective Alt to me, they run on a lot of equipment with a jumper wire from the alt battery post to the #2 terminal.
     

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