1975 Riviera Alternator Going Nuts

Discussion in 'Sparky's corner' started by NotRyan, Jul 7, 2020.

  1. NotRyan

    NotRyan Well-Known Member

    So I did some highway driving today and was enjoying it until my alternator light started coming on. Looked at my gauge and it was at 12v, so I gave it some more gas and then it jumped to 15-16v and it hangs there until I'm idling again, then it drops again. I don't know what's changed but I can definitely tell that it's making the car run rough. In the month or so I've had the car it's always been hanging out above 14v which I know is not ideal. I don't know much about the inner workings of an alternator but if there's a voltage regulator in there or something like that maybe that's not working properly? I'd be more than willing to swap out the alternator for a new one if need be. I guess I'll have to check the battery as well since it may have been getting overcharged.

    Any ideas on what's going on would be very much appreciated. Thanks :D
     
  2. Nailhead in a 1967

    Nailhead in a 1967 Kell-Mnown Wember

    intern voltage regulator gone bad
    you can repair it yourself or replace the alternator

    did the car still start after you shut it off at home?
    don't worry too much about the battery, check the voltage with a real volt meter with the engine running

    somewhere between 13.8 to 14.3 v is what you want when charging
     
    NotRyan likes this.
  3. NotRyan

    NotRyan Well-Known Member

    Sounds good. Voltage regulator sounds like the better option. I haven't checked if it starts but I would assume it would, it was overcharging for 90% of the time. Thanks for the reply!
     
  4. Briz

    Briz Platinum Level Contributor

    I got one on a 77 that charges fine but has the ALT light lit on the dash. Weird
     
  5. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Actually, that's exactly where it should be. It takes a minimum of 13.8 volts to charge the battery. My voltmeter stays at a little over 14 volts at all times.
     
    Quick Buick and Chuck Bridges like this.
  6. NotRyan

    NotRyan Well-Known Member

    Mine often goes above 16v, just today I watched it go from 14v - 16v when the turn signal was on. Plus it'll drop to just over 12v with no other load when idling sometimes until I give it a kick and it goes back above 14.
     
  7. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Something wrong then. Mine is a rock solid 14.2 or so.
     
  8. NotRyan

    NotRyan Well-Known Member

    I got a voltage regulator from the parts store, currently in the process of taking the alternator out. I'm stuck on taking off the rear connector, would you happen to know a trick on how to get it off? [​IMG]

    I can get a wrench on the nut but I need to hold the back one in place and I can't get anything on it.
    https://imgur.com/qsYnbVK
     
  9. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    That's strange, it should not turn. That nut should come right off. That might be a problem right there.

    Just looked at a youtube video. That battery out put stud fits into a square opening so it doesn't turn. Yours must be stripped.



     
    Last edited: Jul 9, 2020
  10. NotRyan

    NotRyan Well-Known Member

    Damn, I figured it was going too well anyways lol. It's a real pain especially since the wire is just twisting itself to death at the same time. I'm considering running to crappy tire and seeing if they have a real thin wrench that might fit over that back part, but I guess last resort would be cutting the connector and putting a new one on. I'd really rather not do that.
     
  11. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    Watch the videos. Hopefully the case hole isn't rounded out.
     
  12. NotRyan

    NotRyan Well-Known Member

    Thanks for the help Larry :) I hope that's not the case. Might have to pull it apart carefully while its still attached. Lucky me :rolleyes:
     
  13. stellar

    stellar Well-Known Member

    I can't open the pic, but there were 2 alternators for that. A 10SI 63 amp and a 27SI 80 amp. If you have the 80 amp alt the strap from the post to the rectifier is probably burnt. You may want to buy another alt as the strap is hard to find. Or you could make your own strap. Cutting the wire may be the best option. Briz, you may have a blown fuse.
     
  14. Nailhead in a 1967

    Nailhead in a 1967 Kell-Mnown Wember

    qsYnbVK.jpg
     
  15. NotRyan

    NotRyan Well-Known Member

    I tried linking the picture but it didn't show up. Thanks :)
     
  16. stellar

    stellar Well-Known Member

    The insulator fits in a square hole and it will need replaced. Usually you can hold the wire with a pair of pliers to loosen it. Saturn made a tool for their mechanics to hold the square part of the post. If you know an ex saturn mechanic he probably has one. It is just a flat piece of metal with a square opening cut on the end.
     
  17. NotRyan

    NotRyan Well-Known Member

    So I got the alternator out at the cost of a broken connector end. Will have to replace that, but yeah that insulator is garbage. I can’t find it on rock auto and Napa has nothing either. I’m gonna call an alternator shop and see if they’ve got anything.
     
  18. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

  19. NotRyan

    NotRyan Well-Known Member

  20. NotRyan

    NotRyan Well-Known Member

    Everything is back together now and working perfectly. That voltage needle doesn't even budge unless under load, as it should be. Thanks everyone for the help!!
     

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