Headlights dimming while using defrost

Discussion in 'Modifications And Maintenance' started by PaulasaurusREX, Dec 23, 2008.

  1. PaulasaurusREX
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    PaulasaurusREX Well-Known Member

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    Anyone have this issue or have seen it on their own car?

    The past couple days i've noticed that while driving, with headlights/fogs on and defrost on the lights seem to dim at certain intervals and the engine starts to stall a little. I've also noticed this while parked and using the defrost with the headlights on where the car nearly stalls out. Using the normal heat setting does not cause the car to want to stall. I'm assuming the defrost fan pulls more juice?

    Its an '02 wrx, the battery is probably 3 years old and it leaks a little every now and then but it still cranks over plenty fine.

    Any ideas? Time for a new battery? What type of tests can I perform to diagnose the problem myself.

    Thanks all
     
    PaulasaurusREX, Dec 23, 2008
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  2. retreif
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    retreif Well-Known Member

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    The AC turns on at certain intervals when in defrost.
     
    retreif, Dec 23, 2008
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  3. WRX1
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    WRX1 _ Staff Member

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    First thing I would do is grab a volt meter and check to see what kinda of volts the alt is putting out with the car running. If your alt is going out, it can't keep up with the extra demand. I HIGHLY doubt it is your battery. You battery is there to start your car, once it is running your alt supplies all your power needs up to the point of drawing more current than your alt can provide.


    Russ

    No, I am not pissed, angry or otherwise. I will be expecting the pm.:roll:
     
    WRX1, Dec 23, 2008
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  4. PaulasaurusREX
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    PaulasaurusREX Well-Known Member

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    Thanks for the info, i'll start with checking out the alt.

    Can someone explain(with pics if possible) where and how to check the voltage. I do have a voltage meter i've just never used it and or checked voltage on anything.

    volt meter noob :)

    Also what volts should I be seeing at the battery and at the alternator?
     
    PaulasaurusREX, Dec 23, 2008
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  5. WRX1
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    WRX1 _ Staff Member

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    You should have 12+ with the car off (at the battery). You should have 13.5+ with the car running at the battery. There should be a stud on the back of the alt where your main power feed wire comes off of it (usually covered with a red boot). You should have the same 13.5+ on that stud with the car running. From there you can kick on your headlights, fogs, defrost, etc and recheck voltages. If you put a load on the alt and the voltage drops off to 12+ (battery power), your alt is not working to good. Like the one in my truck read 14.2 until I turn on my headlights, then it dropped to 12.6 (battery voltage). Swapped out alts and now I am running 14.6 all the time.

    Russ
     
    WRX1, Dec 23, 2008
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  6. PaulasaurusREX
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    PaulasaurusREX Well-Known Member

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    Thanks WRX1, i'll give it a check later today and report back with my findings.
     
    PaulasaurusREX, Dec 23, 2008
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  7. Rexarew
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    Rexarew Subie Girl

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    My car does this. It normally runs at 14+ and then when I stop at a light and idle it drops to 11.3+ or so. :???:
     
    Rexarew, Dec 23, 2008
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