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Ford Alternator w/ External Regulator...?

Discussion in 'The Hokey Ass Message Board' started by CRH, Feb 22, 2009.

  1. CRH
    Joined: Apr 30, 2006
    Posts: 554

    CRH
    Member
    from Utah

    Hey guys, I hope my question isn't stupid! I made the entire harness for my little '27 Roadster, and everything seems to be working fine except the charging circuit.
    The car is running a little 302, and it used an external voltage regulator. I wired the regulator terminals correctly, but didn't use the "I" terminal, since I always assumed that is only for a charge indicator light on the dashboard. I just have the other three terminals properly hooked up (A to BAT, S to Stator, F to Field). Do I need to have the resistance of an indicator light connected to the terminal "I" on my regulator in order for proper charging, assuming all other parts and pieces are working and connected right?
    When I test the new alternator, it only raises the charging to about 12.6 volts, and that requires at least 1200 RPM's. Any help appreciated.
     
  2. coupster
    Joined: May 9, 2006
    Posts: 860

    coupster
    Member
    from Oscoda Mi

    The "I" has to be hooked up to excite the field. Did you try to full field the Alt to see if it is working?
     
  3. coupster
    Joined: May 9, 2006
    Posts: 860

    coupster
    Member
    from Oscoda Mi

    To give you a little more info about that circut, Ford used a 15 ohm resistor in parallel with the indicator light. It was there in case the bulb burned out. You need to use ignition switch voltage for this as the battery would run down if you left voltage at "I" when the engine is not running. Hope I didn't muddy up the explination to bad.
     
  4. 58custom
    Joined: Jan 1, 2009
    Posts: 398

    58custom
    Member

    Coupster is exactly right. Run 12v from the ignition or running accessory supply through a 15 ohm resistor to that terminal whether or not you use a charge indicator light. Use a 1 watt resistor or greater. This works the same when you use a Ford 3G internally regulated alt. I found that out when adding a 3G to my '58 Ford.
     

  5. 24riverview
    Joined: Jan 13, 2008
    Posts: 1,052

    24riverview
    Member

  6. butch27
    Joined: Dec 10, 2004
    Posts: 2,847

    butch27
    Member

    I put a diode in and ran the wire to ACC on the switch.
     
  7. CRH
    Joined: Apr 30, 2006
    Posts: 554

    CRH
    Member
    from Utah


    Holy Moly, thanks for this helpful, straightforward info, people! I'm very grateful, and the reason-why type explanations I like best are what you people have provided. Thanks!! I'll wire the '27 correct tomorrow...
     
  8. CRH
    Joined: Apr 30, 2006
    Posts: 554

    CRH
    Member
    from Utah

    Hey guys, one more question: Is it bad to simply have the "I" terminal run straight from a switchable power source, like the ACC part of my ignition switch? I tried this for fun and it did as stated previously; it excited the field. I'm just wondering if and why a resistance must be part of that circuit...? Is it too much amperage, hence the use of 15 ohm resistor by Ford?
     
  9. 58custom
    Joined: Jan 1, 2009
    Posts: 398

    58custom
    Member

    Well, first, I must correct my previous post. I took a look at my factory data and the resistor is 560 ohms, not 15. Sorry for the bad cheese. The resistor is there to simulate the DC resistance of the charge indicator lamp should that lamp burn out. I have heard of people wiring it up straight without either lamp or resistor but I think I would use a resistor anyways. Another poster mentioned a diode. You have a 50/50 chance of getting that one right. Just get a 470 to 560 ohm 1 watt resistor or a pair of 1K 1/2 watt resistors and put them in parallel, solder on the wires, use two pieces of shrink wrap (shrink one at a time) and there you have your inline resistomathingie for much charging goodness.
     
  10. CRH
    Joined: Apr 30, 2006
    Posts: 554

    CRH
    Member
    from Utah

    That makes sense, no worries. I'm just too "in-the-dark" about why there should be the resistance. I'm scared that maybe it lessens the load on the "I" terminal for a good reason, like protection or something...? I have driven the '27 for the past two days with just a straight wire from the ignition ACC side to the "I" on my voltage regulator, and the alternator charges great. But, does this mean it is overcharging or that my un-resisted wire will eventually burn out the voltage regulator?
     
  11. butch27
    Joined: Dec 10, 2004
    Posts: 2,847

    butch27
    Member

    Put a diode in. You just don't want the voltage to back up to the reg.
     
  12. hrspwrranch
    Joined: Oct 10, 2011
    Posts: 17

    hrspwrranch
    Member

    Do you put the diode on the I terminal?
     
  13. Kenneth S
    Joined: Dec 15, 2007
    Posts: 1,527

    Kenneth S
    Member

    This is how I wire a Ford alternator w/ external regulator, except I delete the amp guage (fire hazard), and use a volt guage. Been wiring then this way for over 30 years with no problems.
    [​IMG]
     
    Last edited: May 24, 2014
  14. TheCreeper
    Joined: Aug 7, 2012
    Posts: 27

    TheCreeper
    Member
    from Louisiana

    It's an old post, but I've been trying to get the charging system fired up on my 48 F1 302 redux for....well, more weeks than I'm comfortable admitting. Thanks for this quote, Coupster...things are working as they should now. I ended up using two 7.5 ohm Brown Devils in series (all I had around here), and EUREKA! Thanks :)
     
  15. This is almost exactly the way Ford wires them when using an ammeter and no idiot light.... The only difference is Ford runs the wire from the 'A' terminal on the regulator to the starter relay, but this will work.
     
    osage orange likes this.
  16. I'm trying to adapt the wiring schematic from a 1977 F-series truck to establish the basic wiring necessary to run in my 351W and AOD. I've got a wiring chart from the '77 F-series truck and the schematic for the 76-77 Duraspark II and all the pieces for the system: Starter, alternator, regulator, distributor, coil, ignition switch, starter solenoid, resistor wire, ignition module (blue insulator), connector plugs and even the voltmeter. Some of this I've figured out from both the F-series schematic and the 76-77 Duraspark II schematic. But I'm not sure where Regulator wires yellow (AT) and green (I) go, and where the resistor wire connects. You've got me baffled regarding the "I" wire, resistors, idiot light, etc. Huh?
     
  17. Mr48chev
    Joined: Dec 28, 2007
    Posts: 33,861

    Mr48chev
    ALLIANCE MEMBER

    Note that the last post above yours was 8 years ago. The problem that you are having is the same problem that every mechanic that wasn't a Ford mechanic in a dealership had when those were a lot newer. There are too many frigging eithers, ors or iff's. Moms 77 has a 300 in it but someone in the past took the electronic distributor out and tossed it in the trash and put a point style distributor in it for that same reason. There are too many variables. There are about three modules that fit the same truck and same engine depending on the mood the day the truck was built. There are some other differences too but I can't remember them. If it is in a hot rod I'd toss that setup and put a point style distributor or an Hei in it and never look back.
     
  18. Yeah, I know I'm resurrecting an old thread, but it was the closest I could search to address the issues I am having. I hope that asking specific questions might lead to specific answers, or at least help me better understand the electrical system of the engine I've rebuilt. Hotrodding is mixing and matching, but so far I'm struggling with the matching part. Anyone else out there know how to tackle this?
     

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