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Old 11-08-2007, 03:31 PM   #1
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Alternator/battery light problem

Lately I have had the alternator light come on occasionally even though all of the voltages appear to be normal (12.3V ICE off, 13.6V to 14.00V ICE on) with the light either on or off. Where in the car are these voltages monitored and the alternator light output generated? I suspect a bad connector somewhere is dropping voltage across it on the way to the ECU or whatever IC monitors the car's voltage.
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Old 11-08-2007, 05:58 PM   #2
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could the belt be slipping?
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Old 11-08-2007, 07:05 PM   #3
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it could, or dirty grounds/loose cables/dirty cables/corroded cables. so check battry cables and clean if necessary, it helps alot if you clean all the grounds you can find. (super fast way to clean: have a drill with one of those small round wire brushes where all the wires are pointed straight down, not in a circle. put in the hole /backside of the contact and let the drill do the work.
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Old 11-08-2007, 07:13 PM   #4
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The voltage regulator in your alternator controls the dash light. I don't have a manual for a Civic, but I imagine the CRX is very similar. On the CRX, there is a wht/blue wire coming out of the alternator that I believe the voltage regulator shorts to ground to turn the light on (the light always has +12V). You may be able to replace just the voltage regulator, but it would mean pulling the alternator apart.
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Old 11-10-2007, 06:36 PM   #5
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Thanks for the replies. The belt's not slipping (that's the first thing I checked), so I guess its a flaky indicator light output circuit on the voltage regulator in the alternator. I'll just live with a voltmeter in the car to check if the alternator light is crying wolf.
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Old 11-14-2007, 07:54 PM   #6
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Lately I have had the alternator light come on occasionally even though all of the voltages appear to be normal (12.3V ICE off, 13.6V to 14.00V ICE on) with the light either on or off. Where in the car are these voltages monitored and the alternator light output generated? I suspect a bad connector somewhere is dropping voltage across it on the way to the ECU or whatever IC monitors the car's voltage.
basjoos,

Have you checked the specific gravities of the battery fluid in each of your battery's cells?
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Old 11-14-2007, 08:58 PM   #7
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heres an even sipler way, take the car to autozone and have them test it...
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Old 11-17-2007, 09:32 PM   #8
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heres an even sipler way, take the car to autozone and have them test it...
VetteOwner,

I took my car's battery to Autozone because my car's "Charging System Problem" indicator light came on. Autozone tested it as "Good." After I took the battery back home, reinstalled the battery, and started the engine, the "Charging System Problem" indicator light still came on.
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Old 11-18-2007, 11:44 AM   #9
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VetteOwner,

I took my car's battery to Autozone because my car's "Charging System Problem" indicator light came on. Autozone tested it as "Good." After I took the battery back home, reinstalled the battery, and started the engine, the "Charging System Problem" indicator light still came on.
take the WHOLE CAR there. they have a machien that they hook up and it tests the charging rate and how many amps of the laternator, checks to see if battery is takign charge(sounds like it is). etc. its free and its acurate.
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Old 11-24-2007, 10:29 AM   #10
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Thanks for the replies. The belt's not slipping (that's the first thing I checked), so I guess its a flaky indicator light output circuit on the voltage regulator in the alternator. I'll just live with a voltmeter in the car to check if the alternator light is crying wolf.
That's what I would do also, more than a few older cars like to flash off a red one but you really don't want to ignore it just yet... Why not get a 2-3 dollar battery post cleaner and take care of those connections, both the posts and the pieces that hook to it, because it's easy and then you know it's not that.

It's worth it, that stupid tool comes in handy later, too.
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