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My '71 has the dummy light for the alternator (and brakes, temp, and oil). I drove my car at night for the first time in a long time, and I noticed that the alt light would come on and fade out on me. This would be either from a dead stop or driving at a constant speed and then "goosing" the accelerator and letting back off (at least that's how I could recreate the situation). The drivability of the car was unaffected, and after coming on, the light would fade back out. Turn signals, etc, worked normally (and no alt light activity).

Now, my question to you all is this: what events does the alt dummy light warn you about, and why might I see this under my specific circumstances? This may have been occuring during the daytime, too, but I don't recall seeing the light. The most recent changes to my car have been the addition of a Pertronix Ignitor and coil. Nothing else electrical has been changed.

Thanks!
 

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my 72 is doing the same thing. have you checked the belt for looseness.randy
 

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Greetings,

My understanding (and it could easily be faulty) is that the Alternator light comes on when the alternator is not providing enough power to keep the car (and all its electrical gizmos) running and then some... I.e. you are no longer charging the battery and indeed might be draining the battery. Once the engine is started the alternator or generator should provide all of the power needed and some ectra to charge the battery.

Given that you have just added a pertronix ignitor and coil (and this happens when accelerating) I would imagine that this has something to do with it. You probably should check your electrical system over (cables etc) just to make sure. I don't know much about this stuff though so someone else might have a more specific area to look at.

I hope that this helps

Z.
 

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My guess is that at night, when the lights are on, your alternator at idle is barely putting out enough amps to satisfy the voltage regulator relay (which feeds your ALT light). It could be (I don't know anything about the pertronix) that when you added the electronic ignition it consumes just enough power that when you turn your lights on at night your alternator no longer produces enough juice.

I would have the alternator and VR checked.

Frank
 

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Mine did that when my second voltage regulator was faulty like the first one I replaced. I'd go to the nearest auto store and test the alternator. If it checks out, then your regulator is the probably cause.

Slade
 

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you could have slighly loose fan belt - don't overtighten it.
 
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