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I just replaced the battery in my '91 Spider. The car starts with no problem now, but the Alternator indicator is on. The instrument panel meter reads 12V. I read in another post that the Alternator light means that there is an imbalance in the system, i.e. that the voltage on one side of the indicator is different than the other side. So it doesn't necessarily mean that the alternator isn't working.

I'm wondering if this just means that the new battery is stronger than it should be and that it will equal out as I drive.

So, do I have a problem or not? Thanks in advance.

David
 

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what made you change the battery?
did the alt. (Battery) light stay on before the battery swop?
the instrument gauge is not really accurate enough to go by, but for instance on my spider (same model as yours) it reads more like 13V on tickover.

If you have a multimeter (now, every alfa owner should have one of those!), you can easily check the alternator is charging correct:
Set the meter to 20 Volts DC, and whilst the engine is idling, put the meter wires on the battery terminals....you should be seeing somewhere between 13.8 and 14.4 volts

let us know.

Another thing is under the hood on the driver's side fender is the main connector block with some thick red wires going into it.
Take off the lid and check the green wire....that is the alt. light wire. Make sure it is clean and tight.

And lastly, just try bliping the throttle a few times, sometimes that turns the alt. light off.
 

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I read in another post that the Alternator light means that there is an imbalance in the system, i.e. that the voltage on one side of the indicator is different than the other side. So it doesn't necessarily mean that the alternator isn't working. I'm wondering if this just means that the new battery is stronger than it should be and that it will equal out as I drive.
Well, yes, the light does indicate that either the battery voltage is > the alternator output (like when the light comes on as you turn on the ignition, before starting the engine), or the battery voltage is < the alternator output (like when the light comes on as you shut off on the ignition, for as long as the alternator keeps spinning). But 99% of when it comes on, it means that your alternator is dead or dying. And no, nothing ever "equals out as you drive" - at least, not for me!

The instrument panel meter reads 12V.
It's hard to read that gauge to the nearest volt. But as spiderserie4 said, the battery voltage should be > 12 with the engine running and alternator working properly. Using a more accurate voltmeter will answer this one more precisely.

Knowing the answers to spiderserie4's questions will tell us more.

Was Alfa using internally-regulated alternators as early as 1991? If so, you should see a part like the one in the photo below screwed to the back of your alternator. That's an integrated brush-regulator unit, which sells for ~$35, is simple to change and may be all that your car needs. The brushes do wear out over time.

 

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Discussion Starter #4
what made you change the battery?
did the alt. (Battery) light stay on before the battery swop?
the instrument gauge is not really accurate enough to go by, but for instance on my spider (same model as yours) it reads more like 13V on tickover.

If you have a multimeter (now, every alfa owner should have one of those!), you can easily check the alternator is charging correct:
Set the meter to 20 Volts DC, and whilst the engine is idling, put the meter wires on the battery terminals....you should be seeing somewhere between 13.8 and 14.4 volts

let us know.

Another thing is under the hood on the driver's side fender is the main connector block with some thick red wires going into it.
Take off the lid and check the green wire....that is the alt. light wire. Make sure it is clean and tight.

And lastly, just try bliping the throttle a few times, sometimes that turns the alt. light off.
I changed the battery because the car wouldn't start anymore. When I pulled the old one and had it tested, it was dead.

Thanks for the information, but my problem seems to have (mysteriously) fixed itself. When I started the car this morning, all the warning lights were off including the alternator light and the volt meter was reading 13.5 v instead of the 12 it had been reading before. I checked the voltage with a voltmeter at the battery, as you advised, and it read 13.68v.

So, I'm not sure what happened, but maybe I should just thank the Alfa gods and quit while I'm ahead.
 

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my problem seems to have (mysteriously) fixed itself. When I started the car this morning, all the warning lights were off including the alternator light and the volt meter was reading 13.5 v instead of the 12 it had been reading before. I checked the voltage with a voltmeter at the battery, as you advised, and it read 13.68v.
Uh, not to rain on your parade, but...

Nothing ever fixes itself - at least, not permanently. You have now had two incidents of charging system failure: the recent light coming on, and probably the dead battery. So it is likely to recur.

It may be something as simple as a loose connector or a worn brush on the part I discussed in post #3 that is working only intermittently. Maybe you can't diagnose it until it starts happening again, but I wouldn't use the car for any long trips until you get this resolved.
 

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I changed the battery because the car wouldn't start anymore. When I pulled the old one and had it tested, it was dead.

Thanks for the information, but my problem seems to have (mysteriously) fixed itself. When I started the car this morning, all the warning lights were off including the alternator light and the volt meter was reading 13.5 v instead of the 12 it had been reading before. I checked the voltage with a voltmeter at the battery, as you advised, and it read 13.68v.

So, I'm not sure what happened, but maybe I should just thank the Alfa gods and quit while I'm ahead.
quite possibly because you gave a bit of throttle and it excited the alternator.
Your charging voltage of 13.86V is excellent and the voltmeter reading 13.5 is good too:)

As Jay suggests though, do keep an eye on things.
perhaps check why the battery died in the first place as you might have a parasitic drain....easy enough to check...you are looking for a 20 milliamp drain....or thereabouts which is normal, anything above is suspect.
here the easy test procedure:
Glad you are back on the road!
 

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