Alternator, voltage regulator Issues

Discussion in 'The Bench' started by matt68gs400, Oct 11, 2017.

  1. matt68gs400

    matt68gs400 Well-Known Member

    Hi all,

    I installed my triple gauges this weekend. Also, my generator light is coming on.

    Voltage across battery is 12.4 with engine off and 12.26 with engine at idle.

    In the car, my gage shows around 12.2 with engine at idle, 13.1 at 2500 rpm amd nothing else on, and close to 11 volts with light, fan, radio, etc on for a full load.

    I have an external regulator. The #2 shows 6.3 volts from regulator to ground. Also, when I bypass (jump) the regulator with a paper clip between F and 3, it takes 25 seconds to get up to 13.8 volts. I’m thinking that by bypassing the regulator, and still having low voltage, the alternator is the problem.

    Thoughts?

    Also, if I replace the alternator,would 100 amps suffice? This car is a daily driver with 455 and the AC will be fixed some day. No big stereo systems or anything else.

    Thanks!
     
    Last edited: Oct 12, 2017
  2. BadBrad

    BadBrad Got 4-speed?

    If yours is stock then it is WAY less than 100 amperes; and if you don't need 100 why bother. I'm running a 1987-ish GM G body unit at 94 amps with integrated regulator. But I have an occasionally run electric fan and an occasionally run big stereo amplifier. The rewiring to eliminate the old external regulator is about an hour worth of work assuming average handiman competence. Mine does not look stock but is a handsome installation.
     
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  3. austingta

    austingta Well-Known Member

    All the parts stores will test the alternator (to some extent) for free, on or off the car. It's one or the other, or both, because that's not enough volts for sure. I'd charge the battery before going anywhere.
     
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  4. matt68gs400

    matt68gs400 Well-Known Member

    Thank you.
    It’s likely original. Or an older model. The manual says it’s 55 Amps output at 6500 generator rpm and 44 Amps at 1500 rpm engine. So maybe anything above 70 Amps is good enough.
     
    Last edited: Oct 12, 2017
  5. yachtsmanbill

    yachtsmanbill Well-Known Member

    Just do a 100A Delcotron one wire alternator and ditch the regulator. GM was using that stuff when Neanderthals discovered fire. 100A will more than cover any future need, and will give you a quick recharge after tuff start when its -20F up here. JMO... ws

    z1.jpg
     
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  6. austingta

    austingta Well-Known Member

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  7. matt68gs400

    matt68gs400 Well-Known Member

  8. austingta

    austingta Well-Known Member

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  9. matt68gs400

    matt68gs400 Well-Known Member

    Thanks. I’ll have to check when I get home and see which “time” the wires will fit. I was at the parts store and they can’t cross reference. I had them check 1976 electra for 12si and it was 12/6 clock, which was in stock.
     
    Last edited: Oct 12, 2017
  10. matt68gs400

    matt68gs400 Well-Known Member

    I want to replace the wire from alternator to battery. I think it’s 8 gauge but might go to 6 gauge. The auto parts store only has black in 6 or bigger. I want colors coded correctly. A little frustrating.
     
  11. badbuik

    badbuik Well-Known Member

    Go to a car stereo shop...
     
  12. austingta

    austingta Well-Known Member

    I think you will need this too. The stock connector has opposing blades. alt wire.jpg
     
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  13. yachtsmanbill

    yachtsmanbill Well-Known Member

    Red stranded that goes to the starter "service post", just as it is now. I just reference the bigger unit as a 100A model. Under the right conditions, 100amps could almost crank a V8; its a lotta juice! I have Manitowoc Motor Machining in town and the guy threw mine together from the OEM spare I had into a 1 wire unit with some parts and it was under $50.00. Runs steady at about 14VDC. I bypassed the OEM regulator but left it in for looks. I'm not sure if the ALT. idiot light still works or not. Ill hafta check on that one! Save the schematic in a file for future reference. That way you can make it way BIGGER to read it easier. Comes in handy.

    I do recall the red and white plug on mine as well. . IIRC, the red goes to the ALT post and the white gets spliced into #4 on the regulator so the alt. is keyed "on". Its barely visible in the pic, but its there. It was such a quick and simple job that I didn't even take any pics while doing it. Ill go out and grab some right now though... ws


    z3.jpg

    z2.jpg
     
    Last edited: Oct 12, 2017
  14. matt68gs400

    matt68gs400 Well-Known Member

    Thanks guys! Say, is the pulley a universal size or does the old one get swapped on the new alternator?
     
  15. matt68gs400

    matt68gs400 Well-Known Member

    271DB72F-594B-4B4D-BED8-24B6170B519D.jpeg 8B6E62A7-2963-440E-A032-021FF650CF31.jpeg
    It states that the “white wire is no longer needed, other end at alt.” But no directions are given. That’s the only confusing part to me.

    Another diagram online shows the white and red wire from the regulator going to the 2 on the alternator.

    The photo I attached seems to be better than the diagram . The brown and blue wires on our Buicks would be the “load side” going to the 1 on the alternator.
     
    Last edited: Oct 12, 2017
  16. yachtsmanbill

    yachtsmanbill Well-Known Member

    With AC the two groove pulleys are all the same. Got some pics of the ALT but its too bad the now working AC obstructs the view. You can see the red wire going to the alt. post and the white to Reg, #4. The others show the idle volts, key on and not running (light on) and idling (light off). I'm good with it for 3 years now! Starter versus header access is a joke that aint funny! ws

    z6.jpg

    z5.jpg

    z7.jpg

    z8.jpg

    z10.jpg

    z9.jpg
     
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  17. yachtsmanbill

    yachtsmanbill Well-Known Member

    After looking the pic you posted with the diode(s), I'm pretty sure my guy bridged one of the internal diode on the diode-trio. I would absolutely forget the ammeter. Model T fords used them and they don't tell you much; a volt meter tells you all you need to know. You don't need 100amps of potential inside the cabin...

    Dodge in their infinite wisdom in the 60's still thought people understood ammeters. So they put an ammeter in the dash that was in reality a voltmeter, just labeled "amps". The ammeter "zero" was a key on not running battery voltage and running with 13+ volts showed a "10 amp charge". A discharge was a dead alternator or low battery (>12 volts). Gotta luv them mopers. ws
     
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  18. matt68gs400

    matt68gs400 Well-Known Member

    Thanks for the pics. I like the vacuum gage.

    No ammeter for me. I just replaced it with a voltmeter.

    What do you mean by Reg. #4?
     
  19. matt68gs400

    matt68gs400 Well-Known Member

    Quite honestly, I’m more confused than ever with the white and red wires, as I have 3 conflicting directions on what to do with it!
     
  20. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD"

    Clip the connector off the regulator wires. There are 4 wires, Blue, Red, White, Brown. Connect the Brown and Blue wires together. Tape off the red wire. Clip the connector off at the alternator. (2 wires, blue & White) You need the new 2 spade connector for the 12 SI alternator. When plugged in to the alternator and viewed from the rear of the alternator, the left one is #1, the right one is #2. The other end of the blue wire gets connected to #1. #2 goes to the charging post on the back of the alternator along with the original red wire. Done.

    This is the new 12 SI alternator spade connector.

    https://www.summitracing.com/parts/...MIp4bX95fs1gIVi2SGCh17tgt-EAQYBSABEgI19_D_BwE
     
    Last edited: Oct 12, 2017

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