Electrical problem.....
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The Classic Cadillac Forum Discussion, Electrical problem..... in Past Cadillac Vehicle Discussion; So I'm relatively new to external regulated alternators. I have had some previous experience, but not much troubleshooting. I recently ...
  1. #1
    Super70DeadSled is offline Cadillac Owners Member
    Automobile(s): 1970 Superior end loader Hearse
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    Feb 2013
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    Electrical problem.....

    So I'm relatively new to external regulated alternators. I have had some previous experience, but not much troubleshooting. I recently got a 1970 Hearse, and it had an 8 year old battery. It ran great, but sometimes it would run the battery down trying to start it. So I just decided to buy a new battery. But at idle, it's around 12.8 or so volts with only the radio on. With the headlights on, it drops to 11.5 or so. I opened the voltage regulator and it's brand spankin' new. I believe that the alternator isn't too old either. There is no singing as if the diodes were bad. And no grinding like the bearings being out. The yellow and blue wires coming from the connector on the alt. going to the regulator are both around 2.5 volts, and the red wire stays consistent from the battery terminal, to the alternator, to the regulator.

    Is the regulator bad?

    I've checked all of the fuses, and did a once over with the wires, (no breaks, or cracks and no corrosion).
    Am I missing something?

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  3. #2
    CADforce69 is offline Cadillac Owners Connoisseur
    Automobile(s): Cadillac Sedan de Ville 1969, Dodge 3700GT '73, Audi A3 1.8T
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    Re: Electrical problem.....

    Welcome to the forum, Super70, Hearses are always interesting and we like to see them preserved or restored

    12,8 does not seems too low at idle. Did you check voltage with engine running at 2.000 RPM? It should be 13,4-14,4 Volts.

    With headlights on, does the "gen" tell-tale light glow?

    Are you having cold starting problems with the new battery?

  4. #3
    talismandave's Avatar
    talismandave is offline Cadillac Owners Master
    Automobile(s): 1987 Brougham, 1974 Fleetwood Talisman, Volvo C70,
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    Re: Electrical problem.....

    Great​ screen name!

  5. #4
    FoxRodder's Avatar
    FoxRodder is offline Cadillac Owners Fanatic
    Automobile(s): 1968 Coupe Deville, 87 Mustang, 00 Mustang
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    Re: Electrical problem.....

    I just put a used alternator in my 68 of the original style external regulator because I needed to give the later model internal regulated one back to my buddy. Once I got everything wired up properly I also found something in the neighborhood of 12.8 at idle which I found odd being used to 13-14 volts with my newer cars. I'm thinking thats just what you get with an oldschool alternator?

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