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Thread: Voltage and heat question

  1. #1
    Registered User lswing's Avatar
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    Voltage and heat question

    So the first time I went out for a drive, noticed my voltage needle fluttering around 13, not the solid 14 I always see. Was around 100 that day, car reading 110. 3-4 other days I've been out in same temps, same thing.

    The one cool day, 75-80 evening, my voltage was sitting nice at 14.

    Needle fluttering seems to have stopped thankfully, but it seems to stay at 13 on these hot days.

    Input? Alternator not working as well in heat, battery? AC taxing the system?

    Thanks in advance...
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    Registered User Other_Erik's Avatar
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    Radiator cooling fans running on high, possibly? What were your coolant temps looking like / were your fans on full tilt in the 100 degree heat vs. lower speed in 75-80 degrees?

    I thought A/C was all belt-driven (except blower motor / air blend door actuators).

    Alternator efficiency would be down slightly, but a full volt off seems a bit much for heat alone to explain.

    In true RS6.com fashion, I'd say run a VAG-COM scan and post up results

    Probably nothing to fret over, unless you start seeing lower and lower voltage readings while running. Toss a solar battery trickle charger on and maybe counteract the mystery Audi voltage drop.

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    If it is north of 85 degrees, I get sub 14, but I also have RNS-E too, that is bound to draw more amps. Xenons, Fogs, A/C and RNS-E (and Escort radar) I will draw less than 14 on cool nights.

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    Speaking of alternators, how long are these things expected to last? The car is now 11 years old.
    How do you know it has seen better days and it is ready or almost ready for a swap?
    Sorry for the thread jack, but felt it is good to know and on-topic.

  5. #5
    Registered User lswing's Avatar
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    Thanks for the input all. My hope is that fans are taxing it more, most are running fast on the hot days, and blowing max AC.

    Nene, just what I was thinking actually. If I'm seeing some fluctuations now, maybe get it fixed before I get stranded. 98,500 miles if that plays into it.

    Coolant temps and everything else seems fine.

    Guessing I just need to fill up with that 100 octane, should fix everything
    Ace/Edge TC - Tozo Trans - MTM TCU - REVO/ME7 tune - Wagner IC's w/ Venair Hoses - Aux Radiator delete - Hotchkis Sways - Hawk HPS Pads - Koni Sport Struts - Scroll KO4 Turbos - Devil's Own WM - 421whp/452wtq on Mustang Dyno - http://www.audirssix.com

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    I don't think mine run that low in the heat. Gimme a couple days and I will be back home.

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    Registered User Jimmy Joe's Avatar
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    If it is fluttering, maybe the brushes are worn out or one or more of the diodes are shot, or the windings are open, or the rectifier... well, I guess your best bet would be to buy a new one, yours should be shot by mileage alone. Not worth to fix'em. And don't forget to change the voltage regulator, just to be on the safe side. My 2 cents.

  8. #8
    Registered User mik15's Avatar
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    i get the same here during the summer, with the AC on, headlights on and RNS-E, i get around 13.7-13.8 according to VagCom. As for alternator life, mine was replaced at 60k miles, and then at 119k miles they replaced the harness and the regulator.
    Ex.: 2004 Audi RS6 C5 ABT, Milltek non-resonated, 19" RS4 B7 rims, RNS-E - SOLD
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  9. #9
    Registered User lswing's Avatar
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    Quote Originally Posted by Jimmy Joe View Post
    If it is fluttering, maybe the brushes are worn out or one or more of the diodes are shot, or the windings are open, or the rectifier... well, I guess your best bet would be to buy a new one, yours should be shot by mileage alone. Not worth to fix'em. And don't forget to change the voltage regulator, just to be on the safe side. My 2 cents.
    Sounds about right. Was only fluttering on first drive after being shipped down to TX from OR...maybe it was just pissed at the heat. Now about a steady 13, or 14, on the dash. Will give it a look with VAG-COM once I find my blasted cable...
    Ace/Edge TC - Tozo Trans - MTM TCU - REVO/ME7 tune - Wagner IC's w/ Venair Hoses - Aux Radiator delete - Hotchkis Sways - Hawk HPS Pads - Koni Sport Struts - Scroll KO4 Turbos - Devil's Own WM - 421whp/452wtq on Mustang Dyno - http://www.audirssix.com

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    Registered User Brav's Avatar
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    Sounds like its on its way out. I would replace.. I noticed my voltage dropping in high heat before it went out all the way.
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  11. #11
    Registered User audiprotn's Avatar
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    I recently got Bosch (rebuilt) Alternator from these guys http://www.maniacelectricmotors.com/150ampboalfo11.html
    So far so good, best price around and good customer service.
    If you order from them, you will most likely receive my "old" one

  12. #12
    Registered User lswing's Avatar
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    Quote Originally Posted by Brav View Post
    Sounds like its on its way out. I would replace.. I noticed my voltage dropping in high heat before it went out all the way.
    Thanks for the input.

    Yesterday was 75 out, no AC running, voltage was stuck at 14 just like normal. So basically when I put the car under max electrical load the alternator just can't kick out enough, alternator worn, wearing down sounds like.
    Ace/Edge TC - Tozo Trans - MTM TCU - REVO/ME7 tune - Wagner IC's w/ Venair Hoses - Aux Radiator delete - Hotchkis Sways - Hawk HPS Pads - Koni Sport Struts - Scroll KO4 Turbos - Devil's Own WM - 421whp/452wtq on Mustang Dyno - http://www.audirssix.com

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    Pic sent.....

  14. #14
    Registered User lswing's Avatar
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    Quote Originally Posted by DHall1 View Post
    Pic sent.....
    Thanks...

    Alternator getting dodgy, might be original, similar issues here.

    http://forum.rs246.com/viewforum.php?f=2
    Ace/Edge TC - Tozo Trans - MTM TCU - REVO/ME7 tune - Wagner IC's w/ Venair Hoses - Aux Radiator delete - Hotchkis Sways - Hawk HPS Pads - Koni Sport Struts - Scroll KO4 Turbos - Devil's Own WM - 421whp/452wtq on Mustang Dyno - http://www.audirssix.com

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