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Replaced alternator, got much higher Voltage

Discussion in 'Civic and CRX - EF' started by Periculum, Aug 14, 2008.

  1. Periculum

    Periculum Senior Member

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    91 CRX with ZC motor.

    I just replaced the original alternator on my car because it couldn't keep voltage (it went all the way down to 7.5v at some points). After replacing the alternator, I get the battery light when I pass 4500 rpm. I checked the voltage and at idle it runs 14.20v and the point that turns the dash light on it is running at 16v. I am used to this car running at 13.50v at idle.

    The alternator came with a note that said Honda approved a smaller pulley than the OEM because some drivers were complaining of low idle voltage. I didn't notice a difference in pulley size when I was trading them out, but I wasn't looking for it.

    A few questions,
    Could the pulley size be causing the higher voltage than the old alternator did?

    Could I have tightened the belt too tight and make it run higher?

    Any other ideas?
     
  2. t3t4delsol

    t3t4delsol New Member

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    I dont understand how your voltage is increasing when you turn your lights on, it will decrease. There is no load on the alternator at idle, when your driving and putting load on it you will be spinning it faster increasing the voltage.

    A larger pully will spin slower and create less voltage. Having the belt to tight will not cause a higher voltage, you should however have atleast a 1/2" in your belt deflection
     
  3. K2e2vin

    K2e2vin Senior Member

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    Bad voltage regulator? I suggest having it tested or taking it back.
     
  4. Periculum

    Periculum Senior Member

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    That was my guess. As annoying as it was to replace this time around, I'm tempted to just replace the voltage regulator instead, just keeping the alternator in the car. Can Autozone or the like 'officially' check the alternator while it's in the car. I'm usually told to take it out of the car so it can be checked.

    to del sol: The voltage isn't increasing due to me turning the headlights on. When the car pops up the battery shaped light on the dash, it is running >16v. That is in the area of 4500 rpm.
     
  5. prpprimo

    prpprimo Hondaholic

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    First off the regulator is built in to the alternator, and its pretty obvious it is defective. Yes, it can be checked/tested in the car. The revolutions of the alternator should not affect its output wether at idle or higher RPM.

    My question is, how does the battery shaped light tell you its delivering 16v? Thats new to me, I would really like to see a photo of that.
     
  6. Periculum

    Periculum Senior Member

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    I just used a volt meter and revved it up until the light would turn on. I am starting to wish I had a volt gauge inside the car. (hmmm, another project to add to the list).
     
  7. jlicrx

    jlicrx Senior Member

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    aftermarket rebuilt alternators from Autozone, Checker, etc. are pretty much garbage - not only do they not work right, they don't last very long - you would be better off going to the junk yard and getting a used OEM alternator
     
  8. Periculum

    Periculum Senior Member

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    Well, fortunately, it's already from a warranty from a while back. So, this alternator is technically free. It's just the installation that I'm doing that's not free. I think I'm just going to have them run the alternator on their test machine before I take it out of the store next time. Not being able to pass 4k rpm is really starting to get to me....
     
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