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Delco Alternator Questions

Discussion in 'Intermediate CJ-5/6/7/8' started by Jeff Bromberger, Nov 23, 2019.

  1. Nov 23, 2019
    Jeff Bromberger

    Jeff Bromberger Quarantined in the Garage

    Dallas Metroplex...
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    Jun 28, 2019
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    My '74 DJ5 had the Motorola alternator. When I swapped out the engine (long story covered elsewhere), I got a 1975 block with the Delco alternator and bracket. I can't tell which model it is (yet), so I would be delighted if somebody could help me with a pointer here.

    With the new alternator, do I have to do any special sort of re-wiring? I really am unsure how an alternator is wired, so this is a learning experience for me...
     
    Last edited by a moderator: Nov 24, 2019
  2. Nov 24, 2019
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    The newer type alternator is a Delco 10SI. These were used on millions of GM and other vehicles, and are a common and inexpensive parts store item. Mad Electrical has an article about how to pick one from parts store stock Catalog but I would ignore all the discussion about picking one with the clocking you want. These alternators are super-easy to clock to whatever direction you want using a special tool (a toothpick).

    The wiring will be different, and simpler, with the Delco. I suggest you compare the 1974 CJ and 1976 CJ wiring diagrams here - JeepĀ® Parts Manuals online - look at the diagrams in their respective TSMs. Note that the '76 diagrams have the V8s and the 6s on the same sheet, and you want to follow the pattern for the 6s - they came with the Delco alternator.

    Be wary of upgrading your alternator if you have an ammeter. With the ammeter, all the charge current goes to the dash, through the ammeter, and back from the dash to the battery. The ammeter and its wiring is not up to supporting a much more powerful alternator.

    Very much worthwhile to have the more reliable and much more available Delco alternator over the Motorola if you have a choice. Looks like the alternator swaps sides in '75, and it's likely you'll have to use everything from the front of the '75 engine if you go with that configuration.
     
    Last edited by a moderator: Nov 24, 2019
  3. Nov 24, 2019
    Jeff Bromberger

    Jeff Bromberger Quarantined in the Garage

    Dallas Metroplex...
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    Jun 28, 2019
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    202
    My jeep is "wired" for the Motorola alternator and I didn't know there were such big differences between the two designs/manufacturers.

    THANKS for the link to Mad Electrical. They had a killer article on the Delco-Remy alternators. Somehow, we need to make a sticky link to that - it answered all of my questions first go round.

    Yeah, I have the factory ammeter in the dash - all of the Postal Jeeps had them. I will either replace it or perhaps run a super thick wire that direction if I want to keep the stock look.
     
    Last edited by a moderator: Nov 24, 2019
  4. Nov 24, 2019
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    Alternators do mostly all work the same. They all create 3-phase AC which is rectified to DC to charge the battery. They use the battery voltage as a signal (feedback) to the voltage regulator (VR). The VR changes the current through the alternator windings based on this signal, which regulates the alternator output.

    The main difference is the elimination of the external regulator. Wires between the alternator and regulator go away. I think the exciter wire works differently on the Delco too; it needs to be connected through a resistance wire or a diode, unlike the Motorola which connects to the starter solenoid?

    Even if you upgrade the wires, the ammeter itself is not capable of passing more than say the 35 amps that the wimpy Motorola alternator produces. All of the current goes through a shunt (essentially a calibrated wire) inside the ammeter and the voltage drop across this shunt is what moves the ammeter needle. Everything will be fine until you have a flat battery and the new Delco alternator tries to charge the mostly discharged battery at 60 amps or whatever and the ammeter bursts into flames (probably an exaggeration, but you get some kind of smoke and/or fire in the gauge).

    I'd also point out that you probably won't be able to buy a "standard" 10SI at 35 amps or such. All the replacements available will be 60 or 80 amps, at least in my experience.

    Lots of advice online about how to bypass the ammeter and replace it with a voltmeter. Mad Electrical has a page about this too. Catalog
     
    Last edited: Nov 24, 2019
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