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Charging issue 911SC
Car has new battery and new (reman) alternator
Car not running battery shows just over 12 volts Car running voltage rises to well over 13 Car can be shut off, started no prob again and again, lots of power. Everything fine, fine , fine for say 5 minutes of idling Then all of a sudden voltage drops FAST 11, 10, 9 stays there at 9 but car still runs with tach bouncing, lights dim. Sporatically car goes back to normal and battery charges right up car will not restart without a jump New battery will slowly rise back to 12 but car wont start- voltage dumps to @4, Not enough to turn the starter Same prob with both new and old battery Did I put in a bad reman alternator? Thoughts?
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-Vinny 1983 911SC |
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10-12-2006, 03:00 PM
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Join Date: Apr 2001
Location: Linn County, Oregon
Posts: 48,527
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I'm not sure when the factory moved to the "internal" Voltage regulator...but it sounds like your problem could lie there. Also, check your ground straps...the one underneath....
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"Now, to put a water-cooled engine in the rear and to have a radiator in the front, that's not very intelligent." -Ferry Porsche (PANO, Oct. '73) (I, Paul D. have loved this quote since 1973. It will remain as long as I post here.) |
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10-12-2006, 04:07 PM
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Join Date: Jun 2004
Location: Rio Rancho, New Mexico
Posts: 1,325
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I would be concerned that the large positive wire from the battery to the starter is damaged somewhere and going to ground.
For a fully charged battery to drop "fast" to 9 volts indicates a significant load that only a large wire is capable of delivering, the positive wire from the battery. I would disconnect it at the battery and at the starter, then check for any kind of low resistance to ground. I would definitely push and pull the wire while looking for a ground. Another indication would be a large spark when connecting a fresh battery. If the wire at the starter to the battery checks out ok, I would look at the wire from the starter to the alternator. Same story push and pull, maybe even remove the wire and inspect it.
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DOUG '76 911S 2.7, webers, solex cams, JE pistons, '74 exhaust, 23 & 28 torsion bars, 930 calipers & rotors, Hoosiers on 8's & 9's. '85 911 Carrera, stock, just painted, Orient Red |
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10-12-2006, 04:42 PM
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Join Date: Feb 2004
Posts: 1,317
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I think if the battery cable shorted to ground anywhere at the very least there would be lot's of buring wire smells and quite possibly a fire within seconds.
It sounds more like a bad ground somewhere or a problem with the alternator once it get's heated up. After you've checked all the grounds take the alternator out and have it bench checked at an alternator shop.
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Clifton Brown https://www.mancalamarketing.com |
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10-13-2006, 05:33 PM
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Join Date: Oct 2002
Location: Minneapolis, MN
Posts: 1,226
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My 1979 SC had a similar problem. Voltage regulator cured it. Easy to replace.
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Thanks, Mike When I was a kid, I didn't want a stupid pony, I wanted a PORSCHE. 1970 911T Coupe, 1979 911SC Targa Euro, 1971 Honda CT70 HK Trail 70 (the ultimate in two wheeled transportation) |
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10-13-2006, 08:08 PM
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Quote:
Thanks Cliff, you were right
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-Vinny 1983 911SC |
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10-16-2006, 05:56 PM
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1983 911SC
