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Registered
Join Date: Nov 2005
Location: Auburn, Wa
Posts: 17
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charging problem
well after reading 13 pages of searches for "alternator" i decided to ask. on sunday i was gonna take the 944 over to my parents house for my dads birthday, and i noticed immediately after i started it that the lights were dim(headlights, dash). well i took off anyway and about a mile down the road the headlights were really dim and the radio was turning on and off, so i pulled off to the side of the road and turned it off. i turn it back on and finally notice the alt. light does not come on when the key is in on position. i called my dad and he came with another battery and a DVM. the voltage of the old battery was 11.60v and we tested it off of the large cable on the alternator and it was the same. we then tested it from the small wire (blue?) with the key on engine off and it was 10.68v. i just had the alternator rebuilt about 2 months ago. also since i've owned the car the alt light would come on while starting but wouldn't go out until you blipped the gas just a little bit.
From what i have read you only need 2v on the (blue) wire to excite the field, i had 10v I have not tested the alt light bulb what is the chance that is it or the windings in the alternator? Thanks Todd
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1983 Porsche 944 1966 VW Bug |
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12-17-2007, 10:53 PM
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Old 928 Guy
Join Date: Oct 2005
Location: Maryland
Posts: 408
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I'm not sure if it's exactly the same, but I just recently learned on my 928 that the light bulb for the alternator idiot light is actually part of the alternator activation circuit, so if the bulb fails the alternator does not come on unless the engine is really revved.
I had put a new alternator on it, started it up, and read the same 11.6V you described. The catch for me was that I had also removed the instrument cluster (and thus the alternator lamp) as part of another project on that car. I haven't looked at the 944 schematics but there's a reasonable chance that the alternator warning bulb coulc be involved.
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1990 C2 Cabriolet Guards Red  '81 928 Zinnmetallic Project Car (sold)  )'87 944na Maraschino Red Metallic (sold) )
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12-18-2007, 05:48 AM
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Registered
Join Date: Jun 2003
Location: Phoenix, AZ
Posts: 1,327
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the light is part of the circuit but increasing rpms won't help.
the bulb needs to be replaced and the batt fully charged with a charger.
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87 951, K27/6, Almond Beige, 17" Turbotwist 87 944S, alpine white, 5sp died a violent death 84 944, silver/brown, auto, gone but not forgotten "may the force be with you" |
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12-18-2007, 08:31 AM
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Trying to work for parts!
Join Date: Oct 2006
Location: MO
Posts: 1,760
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sounds to me like 2 different problems. Did you figure out why your power slowly went away? I dont about the early cars so can't say anything to the alt light.
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86 Metallic Grey 85.5 Metallic graphite - Gone |
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12-18-2007, 09:14 AM
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Old 928 Guy
Join Date: Oct 2005
Location: Maryland
Posts: 408
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if the alternator was not "activating" then wouldn't you eventually drain the battery down with the headlights on?
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1990 C2 Cabriolet Guards Red '81 928 Zinnmetallic Project Car (sold) )'87 944na Maraschino Red Metallic (sold) )
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12-18-2007, 11:26 AM
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Registered
Join Date: Jun 2003
Location: Phoenix, AZ
Posts: 1,327
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yes, that's the point of seeing the lite when the key is in the on position and the lite is off when the car is started.
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87 951, K27/6, Almond Beige, 17" Turbotwist 87 944S, alpine white, 5sp died a violent death 84 944, silver/brown, auto, gone but not forgotten "may the force be with you" |
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12-18-2007, 12:49 PM
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