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Thread: VW Owners / Dimming lights

  1. #1
    Low Bitrate TheSpatulaOfLuv's Avatar
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    VW Owners / Dimming lights

    Hi all

    This questions really is geared for VW/Audi drivers due to the unusual nature of the VW electrical systems, however anyone with high power draw experience are surely welcome to contribute.

    I'm on my second bug, and as with my first one, as well as the wife's Jetta, I've noticed that the lights dim on these cars horribly, even before adding amps, computers, cappuccino makers, etc. It seems as if the TDI's lights dim more than the gassers. I'm a bit concerned, because I've tried a few things and can't seem to lick the dimming. I'll describe the setup the best I can:


    Direct from Batt:

    4g wire lead, double fused to 1f Cap, then to distribution block, which uses 8g wire to each amp. Amp1 = 500W Kenwood Excelon, Amp2 = 250W MTX. Each amp is using 8g ground, to a common 4g ground point that is bolted to the chassis, using the bolt that holds in the rear seatbelt. Prior to mounting the ground, I dremeled the area around the bolt to remove paint/coatings, ensuring good contact. As an added measure, I've added a ferrite cube to the power lead, prior to the capacitor in hopes of reducing noise from the inverter, which it did help.

    As stated, Carpc is a laptop running off an inverter, and eventually, I'd like to integrate the inverter power lead to the distribution block and switch it, but I'm concerned about doing it until I straighten out the dimming issues.

    Here's the crux of the situation. I really don't think it's healthy for the carpc to have the car fluctuating power like this when the bass hits. I've read about grounding kits on vwvortex, but most of the posters there don't use scientific results to prove the upgrade is worth the expense. Theoretically, it should straighten out the problem, but I don't want to run into any problems with VWOA with warranty issues by added wires in the engine compartment. I've been smart enough to avoid problems by running my own power lead to handle my stereo, bypassing any VW wiring harnesses. I've talked with the dealer about the lights dimming, and was told this is normal and within specification (even with the stereo bumping, things measured out ok).


    To sum it up:

    Are the grounding kits the ticket, or should I be looking for an uprated alternator? As far as an uprated alternator, would something from a VR6 provider higher output and perhaps bolt right on? If not, where would I source a higher output alternator?
    -=-
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  2. #2
    MySQL Error MatrixPC's Avatar
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    Do you know what kind of output/spec does the alternator generate?
    Ground kits some what help, but I don't think it hurt to have one. You don't have to run 10 wires on the engine bay like a spider web. Just 2 or 3 will be enought (batter - to Frame by the battery, batter- to alternator mount bolt/screw, and battery-to tranny). Adding wires that way will NOT void the factory warrantee because you are just improving existing wires. I have it install on my Supra and Matrix.
    The next one you have to look to before replacing the alternator is the battery. What is it capacity? The PC doesn't survive cranking in my Matrix with stock 300+ CCA battery. Once replace with an Optima Red Top battery (910CCA), the PC survive cranking as well as no dimming when the the window roll to the top/bottom when you still hold the switch.
    Most/all newer car has a very cabable alternator.
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  3. #3
    FLAC
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    I have a Jetta TDI. I havenít noticed any dimming lights. The output of the alternator is relatively low (I think 90 watts) considering it has things like heated seats. Regardless with everything running havenít noticed any problems. My main power cable is 4 gauge. I have two amps one for the main speakers and a modest subwoofer amp. I donít use much bass and donít have caps or anything.

  4. #4
    Constant Bitrate cbergeron's Avatar
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    VR6 Alternator is not the solution...

    We have a 2000 VW Jetta GLS (VR6) prototype vehicle, and I can tell you first hand that 'upgrading' to a VR6 factory alternator is not a great idea. It _might_ give you a little more power than what you have now, but keep in mind that the VR6 Engine is generating more power, and thus can be attributed to the alternator's higher output. I tend to think that your best bet at this point is to have your existing alternator re-wound for higher current output.

    You may also want to consider adding a secondary battery and a Car Audio grade Voltage Regulator. Note: A car audio grade Voltage Regulator is _NOT_ the same thing as a 7805 voltage regulator "chip / IC".

    Hope this helps...!
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  5. #5
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    I will second the VR6 alternator comment

    a lot of output of an alternator (and it's not watts, it's amps) depends on the motor and it's speed (RPM).

    even with my factory alternator and ABSOLUTELY no radio or system of any kind I have dimming issues, but I am also running underdrive pullies and have taxed my alternator pretty damn hard (3 seasons of SPL competitions on the stock alternator - upgrading it would have moved me into a differnet class).

    Upgrade your wiring like others have suggested. Getting to the alternator on the VR6 requires removing the entire front clip of the car (which is why I haven't done it yet - going to try to get to it this time around though - as well as having the alternator rewound) Upgrade your battery (if you haven't already).. As for voiding the warranty, if you have already run stereo in the car they can get you on warranty....

    now now, I know most people will tell me that they have to prove it to not cover it, but there is another side to the law.....the dealer is protected as well....go ahead and upgrade what you can and be done with it


    a lot of VW owners have computers in their cars (I'm one) and have the dimming issues (I am also one of those) and have noticed no ill effects on my computer.....and I was running WAY more power than you have currently and was on a single battery and stock alternator....
    Jan Bennett
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  6. #6
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    I also had a question about alternator, and from searching online found that there are higher amp alternators specifically made to replace the original ones (I think the max one I saw was 110 Amp). Would that do the trick, instead of rewiring?

    And I am glad to know that my car is not the only one that dims its lights... do you people have that issue when closing already closed windows?

  7. #7
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    a lot of times having the alternator rewound is cheaper than buying an all new higher amp one.

    as for cloing already closed windows....you are putting a pull on the system by closing the circuit....no matter if it's already closed or not
    Jan Bennett
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    Please post on the forums! Chances are, someone else has or will have the same questions as you!

  8. #8
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    Quote Originally Posted by Red GTi VR6
    as for closing already closed windows....you are putting a pull on the system by closing the circuit....no matter if it's already closed or not
    I am aware of that, but that's the only time my lights dim, normal operation does not affect the brightness

  9. #9
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    are you stopped while you do this? or have you noticed it while you are driving and try to close already closed windows??

    if you only notice it while you are stopped then that would explain it. Your motor is not turning the same RPMS that is is while you are driving, thus the alternator isn't putting out the same amperage.

    the deal is that your window motor is an electric motor. Even though the window is already up (or down even) you are still putting current to that motor telling it to spin. Since it trys to spin but it can't (since the window can't go any further) you are actually drawing more current. Make sense?
    Jan Bennett
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    Please post on the forums! Chances are, someone else has or will have the same questions as you!

  10. #10
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    BTW TheSpatulaOfLove, don't actually but a grounding kit. You can make your own, all it takes is some wires. All those kits are are wires cut to length with some ends on them and priced to reflect someone else doing the cutting and crimping. That's all stuff that you can do on your own. Regular stereo power wires should be fine, hell, you can even use welders cable if you can find a welding supply store around you. 1/0 is 1/0, it should all have the same strand count. Welders cable will be just as pliable in some instances as some car stereo 1/0 and will be much cheaper.
    Jan Bennett
    FS: VW MKIV Bezel for 8" Lilliput - 95% Finished

    Please post on the forums! Chances are, someone else has or will have the same questions as you!

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