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The battery in my '72 Chevelle started to boil over and it eventually died. I replaced the battery and the alternator with one from Autozone, figuring the internal voltage regulator went bad. I then realized I also had an external voltage regulator, so I replaced it. I knew I didn't need both so I searched online and changed my wiring per the guidelines detailed at http://www.chevelles.com/techref/ftecref14.html. This scenario is almost identical to Hoppy's posting of Oct. 6.

The problem I have now is that the generator light stays on. I have the standard idiot light and an Autometer ammeter that the prior owner added. I do not have SS gauges. I am looking for any suggestions.
 

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I recently went thru this with my 71' truck and it turned out the alternator was bad. If you bought a rebuilt one for $25, sometimes it takes 2 or 3 times to get a good one!. Take it back and have it tested. It's always a good idea to test it Before you leave the part store when buying a cheapie. My 2 cents!
 

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king72 said:
I replaced the battery and the alternator with one from Autozone, figuring the internal voltage regulator went bad. I then realized I also had an external voltage regulator, so I replaced it.
First what kind of alternator did you install on the car? You can't use this
http://www.chevelles.com/techref/ftecref14.html. with a externally regulated alternator, it has to be a internally regulated one. Externally regulated alternators have the 2 prongs like this l l Internally regulated alternators have prongs like this - - Post back with type of alternator and we can go from there. Your original problem with the battery boiling over points to high charging voltage, which could have been the external voltage regulator. Normal voltage at the battery with the car running at a fast idle is 14-14.5 volts. Externally regulated alternators unregulated will produce 16+ volts.
 

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My new alternator has vertical prongs ( l l ) and not flat prongs ( - - ), however, I always thought that if the wires entered the alternator on the side, and not in the back, that meant there was an internal voltage regulator. Also, the salesman at AutoZone stated that the alternator has an internal regulator, but I don't know how much he really knows. Their website does not specify. Maybe I should take the alternator back to AutoZone to have it tested and see if I can confirm if it has an internal regulator. I need to know for sure about the regulator before proceeding and making sure the alternator is working properly is just as important.
 

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king72 said:
My new alternator has vertical prongs ( l l ) and not flat prongs ( - - ), however, I always thought that if the wires entered the alternator on the side, and not in the back, that meant there was an internal voltage regulator. Also, the salesman at AutoZone stated that the alternator has an internal regulator,
All Si series alternators, the wires enter from the side. I wouldn't trust the guy at autozone. If it looks like this in the pic below it is a externally regulated alternator



Heres a pic of a internally regulated alternator below



If its a externally regulated alternator and you want to use it, you will have to unmodify the wiring at the regulator and return it to factory spec.
If its a internally regulated alternator, remove the regulator and make sure the wiring is modified as in the link http://www.chevelles.com/techref/ftecref14.html.
To make sure either type of alternator is working, check the voltage at the battery with the car running at a fast idle, it should be between 14-14.5 volts with a fully charged battery and the GEN light should be out.
 

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Discussion Starter #6
My alternator looks exactly like the top photo, so I guess it does not have an internal voltage regulator like I thought. Therefore, I need to return the wiring back to its original arrangement. When I previously checked the voltage with this arrangement, it surged between 14 and 16 volts and the headlights brightened with each surge. Even though I just bought a new voltage regulator, it appears that it may be bad based on this. I suppose something else could make the voltage fluctuate, but I am not sure what that might be. I guess my next step should be to return the voltage regulator and get a new one - maybe they can test it at the store.

Thanks for your help. I greatly appreciate it.
 

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Just make things simple and get an internally regulated alternator. Ask for one from a mid to late 70's pickup (or probably any car for that matter) and you'll get a 10SI which will work great for a fairly stock car. Just look till you find one that's got the connection as posted in the bottom picture. I consider the 10SI as the workhorse of alternators - cheap and reliable - so you just can't go wrong with one.

If you're looking to run electric fans then I'll have to find a reference to point you to a 12SI or a CS130 to handle the extra current.

If you're set on using the externally regulated alternator then post back and we'll go through some troubleshooting steps for it.

Peter
 

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How can I check to see if my external regulator is working. Seems my amp gages shows a discharge with headlights on and eng running
Steve
 

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What amp alternator do you have? Is this at idle or above idle? Are you using any underdrive pulleys? Anytime you see the amp gauge in the discharge side (assuming is working correctly) it is the same thing as a GEN light being on and you are running off the battery. To be sure, check the voltage at the battery with the car running at a fast idle, it should be between 14-14.5 volts with a fully charged battery.
 
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