rev engine, lights get brighter

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  1. #1
    SupraForums Member Junked87Turbo's Avatar
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    rev engine, lights get brighter

    Whenever I rev the engine the lights get brighter. They say that is a sign of the alternator being bad, but could it be the battery because I just got a brand new alternator from Autozone yesterday. My belts are pretty tight too.

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    SupraForums Member 91T4's Avatar
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    Slight > in brightness is expected....should not be severe. Do you have other electronics running?
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    SupraForums Member XTC Dynamic Supra's Avatar
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    its not the battery. turn the car on...take the battery out while the car is on. It will stay on if your alternator is good. then try to rev the engine. It has to be your alternator.

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    Just throwing this out there. It could be your voltage regulator, unless the supra alt has it built in. Also it very well could be your battery. If you alt went bad and you ran it for a while its possible to screw up your battery, I would have it tested. Same thing happened on my other car a few months ago.

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    SupraForums Member ma71supraturbo's Avatar
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    Originally posted by XTC Dynamic Supra
    take the battery out while the car is on. It will stay on if your alternator is good. then try to rev the engine.
    That could screw up your electronics

  7. #6
    helps you jump higher AZmkiii's Avatar
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    Originally posted by XTC Dynamic Supra
    its not the battery. turn the car on...take the battery out while the car is on. It will stay on if your alternator is good. then try to rev the engine. It has to be your alternator.
    Unplugging your battery while it was running could cause major problems

  8. #7
    grankor
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    What else do you have installed electronic-wise? There is a ton of electric crap that runs on our car.

  9. #8
    SupraForums Member kevman05's Avatar
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    Originally posted by AZmkiii
    Unplugging your battery while it was running could cause major problems
    naaa kant be...dats the only effective way in my opinion to see if your alternator is good. unplug the battery while the car is running, if the car stays running, and u can rev it...ur alternator is good.

  10. #9
    boost freak drjonez's Avatar
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    Originally posted by XTC Dynamic Supra
    its not the battery. turn the car on...take the battery out while the car is on. It will stay on if your alternator is good. then try to rev the engine. It has to be your alternator.
    NOT a good idea....this can lead to a severe voltage spike in your car's electrical sys (think about it- you're removing the primary load...).....
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    boost freak drjonez's Avatar
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    Originally posted by kevman05
    naaa kant be...dats the only effective way in my opinion to see if your alternator is good. unplug the battery while the car is running, if the car stays running, and u can rev it...ur alternator is good.
    once again, completely false. i test automotive electrical systems for a living, that very test is the most destructive test we do.....

  12. #11
    Schmleff
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    the alternator needs current to make its magnetic field. If you take the battery out and there is enough electrical load elsewhere, the car will die.

    I vote battery, or battery connection. Do you own a volt meter?

  13. #12
    boost freak drjonez's Avatar
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    heh....you have that a bit backwards....

  14. #13
    Shawndude
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    http://www.cygnusx1.net/supra/librar.../ch/CH_01.html

    And whatever you do, don't disconnect the battery with the engine running. That is a damaging cave-man method, that probably originated in the 70's before computers.

  15. #14
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    ALTERNATOR

    THE REGULATOR IS DONE.
    CHANGE THE ALTERNATOR NNNOOOWWW
    BEFORE YOU GET INTO DEEP SH..
    I'VE HAD THAT PROBLEM BEFORE.

  16. #15
    Just say no to Supras conundrum07's Avatar
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    Originally posted by djmtpocket
    Just throwing this out there. It could be your voltage regulator, unless the supra alt has it built in.
    I think all modern alternators have bulit in regulators.
    1989 Toyota Supra NA-T

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    Republican Ckanderson's Avatar
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    OMG YOU
    BETTER JUMP ON
    REPLACING THAT
    ALTERNATOR, OH SH..

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    We have a discussion once a day on batteries, alternators, and starters. And once a day someone tells another person to disconnect the battery to check the alternator. While this was a good "test" with a pre 80's car, this can cause major problems with newer cars, as many other people have already stressed many times. If you want to check the alternator or voltage regulator, do like we did at Interstate Batteries. Invest in a cheap little voltmeter, connect it to the battery and watch for more than 13.8 volts....I'm sure someone knows exactly what a Toyota alternator puts out. If you have any large fluctuations then it could be the regulator. I'm betting that you need to take the battery out and give it a nice little charge overnight at 2amps works great. Allow the battery to stablize for 3-4 hrs if you want to get an accurate voltage reading. Otherwise stick it in, it should be fully charged.
    Batteries are used to crank the starter, dampen the voltage coming from the alternator to prevent voltage spikes and we use it to power the car when the engine is off. Alternators power the whole electrical system with the engine running and recharge the battery, keep in mind it takes a long time to recharge not just a 20-30 min drive. I've said this before but 50-60% of the batteries we recieved as cores were indeed good batteries. Which in turn we sold as used batteries. One of the best tools to use when checking yoru battery is a 3 dollar hydrometer, and its simple to use.

    Jeremy

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    SupraForums Member XTC Dynamic Supra's Avatar
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    dang dont jump on my back on this....im not telling the guy to drive the car around with the battery out. its a matter of disconnecting the battery and one rev. yes you can have a spike but tell me you guys have never tested someones or even your own alternator this way. shit this is the way to do a ghetto jump start. Tell me if your stuck somewhere with a dead battery. Your buddy happens to be there with a running car and a battery that works. tell me you wouldn't take his battery to start your car then drop back your battery once it's started. Believe me...You'll do it.

  20. #19
    Republican Ckanderson's Avatar
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    we are just saying, i would rather call AAA and have a jump, then ruin my ECU and deck, and e-manage, and profec....
    My HID GB has been shut down by SF staff due to a site sponsor confliction. Everyone who paid will be getting their kits without a question. Please PM me for more information.

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  21. #20
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    We're not ganging up on you, but listen to what you just said......Ghetto. And he;s not stuck on the side of the road with no other options. Lets try to get people to do it the right way first, it may cut down other problems. Not trying to start anything, I just want people learn the right way.

    Jeremy

  22. #21
    NeverNZ
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    mine does that to, but only slightly, if you think its a big deal, why not put in the mr2 alternator, there are 1 or 2 mr2 alternators that have a higher current then ours

    remember, these cars are old now, so it is also very likely that the alternator could be dying, especially if you have an aftermarket stereo with amps and it draws a high current. My alternator in my old car died with my system putting to much of a load on it, and it was only a 1997.

  23. #22
    Schmleff
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    Originally posted by drjonez
    heh....you have that a bit backwards....
    ah, no, I don't.

    It is one of two things, the battery is dead, or the regulator is not providing enough field current to generate the required output at low rpm.

  24. #23
    ***ified? p5150's Avatar
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    The regulator is bad. DISCONNECTING THE BATTERY WHILE THE CAR IS RUNNING IS A BAD IDEA. Sorry dude, hate to :uzi: but that is just WRONG. If the alternator wasnt producing enough current, that test would let you know - if you didnt jack up something in the process. But it IS producing enough current, its just not REGULATING the current. The voltage regulator is built into the alternator.
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  25. #24
    Schmleff
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    I am confused as to who is talking to who now.

    Pulling the cable while running is not a good idea cause the battery is the systems "shock absorber"

    field current controls alternator output

    regulator controls field current

    regulator should read bus voltage

    battery takes up slack for the alternator when it cant make enough output at low rpm because of lack of motion in the magnetic circuit

    the post before me is right, the regulator could be stuck providing too much field strength.

    It took me longer to type this than it would have taken for me to test it with a dmm and have the answer.

  26. #25
    Shawndude
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    Originally posted by XTC Dynamic Supra
    dang dont jump on my back on this....im not telling the guy to drive the car around with the battery out. its a matter of disconnecting the battery and one rev. yes you can have a spike but tell me you guys have never tested someones or even your own alternator this way. shit this is the way to do a ghetto jump start.
    I've done this a long time ago, on a friends car. Disconnecting the battery with the engine running was fine, once we reconnected it, we blew out majority of the lights, blew out the computer and fried the ignition.

    DON'T DO IT, it's just not worth it. It's a dumb test, when just looking at the brightness of your lights can tell you if the alternator is charging fine.

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