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Registered
Join Date: Aug 2000
Location: Deep in the bowels of UCLA hospital
Posts: 2,316
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When revving engine...lights gets brighter
is this a sign of a bad battery
or an alternator MJ |
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08-02-2001, 10:35 AM
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Registered
Join Date: Feb 2001
Location: Scotch Plains, NJ
Posts: 346
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Probably the alternator brushes. Easy to replace. How many miles on the car?
------------------ Josh Black on Black '84 Carrera |
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08-02-2001, 10:37 AM
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Registered
Join Date: Nov 2000
Location: Ashburn VA.
Posts: 667
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Time to check the alternator.
GB83SC |
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08-02-2001, 10:43 AM
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Registered
Join Date: Dec 1999
Location: TX USA
Posts: 9,804
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Check your system Voltage with a digital multimeter, both at idle and at 2500 rpm and 4000 ... it should be between 13.2 Volts and 14.5 Volts. If alternator output is low at idle, but OK at higher rpm, your car may need the 91 Ohm, 5 Watt resistor mod accross the alternator warning lamp socket.
------------------ Warren Hall 1973 911S Targa |
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08-02-2001, 12:01 PM
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Registered
Join Date: Feb 2001
Location: Jamul, Ca
Posts: 251
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My alternator light stays on for the first mile or so of driving. Once I get the rpms up to 3K or so it goes out and stays out. Is this normal or do I need the Early S Man response fix?
------------------ Dan S. 1974 911 Targa |
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08-02-2001, 12:11 PM
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Senior Member
Join Date: Nov 2000
Location: Great NorthWest
Posts: 3,944
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The alt. light staying on sounds like bad grounds to me. Kicking it over 3k is overcoming the rustistance, so to speak!
Bad brushes commonly cause the bright light syndrome. I had my alt. rebuilt and went ahead and bought a new battery anyway. The combination sewed up all the problems. By the way: when you have the alt brushes replaced, ensure that you tell the tech. to look at the commutator (i.e. what the brushes ride on). If the commutator has to be ground down, and it is only good for one more go, consider getting a "new" or nicely rebuilt unit that has solid windings, commutator, brushes, and bearings. You don't want to pull the fan/shroud/wires again at a sooner-than-later date. Jw |
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08-02-2001, 12:43 PM
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Registered
Join Date: Dec 1999
Location: TX USA
Posts: 9,804
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Dan,
It wouldn't hurt to check & clean agrounds around the engine/trans & battery, but if you ever see a flickering alternator lamp at speed ... it is either a failing Voltage regulator, or worn brushes! The brushes amd slip-rings in an alternator do not carry anywhere near the high current of brushes in a generator! They only carry the excitation current for the field winding which creates the rotating magnetic field, not much over an Amp or two ... as the variation in field current by the regulator is what does the regulation, per se! If your alternator warning lamp GLOWS DIMLY AT NIGHT, even when system Voltage is fine, then you probably need the 91 Ohm 5 Watt resistor mod. soldered accross the lamp holder. ------------------ Warren Hall 1973 911S Targa |
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08-02-2001, 03:20 PM
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