Battery going dead - Impala Tech
Electrical & Wiring Troubleshooting electrical problems

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post #1 of 5 (permalink) Old 02-17-2019, 01:23 PM Thread Starter
Join Date: Nov 2017
Location: SE PA
Posts: 28
Battery going dead

So we recently installed a Headlight Enhancement kit from AAW and this corrected the dimming/cutting out of the headlights. Last week my son was out in the car and it just died. He had it towed home and I put a battery in and fired up. Well yesterday same thing happened to me. Got it home and tested battery while engine running and only getting 12.5 volts at battery. Tested battery at idle and 2500/3000 rpm. It has new voltage regulator(as of yesterday), new battery(as of yesterday) and an alternator(autozone) that was installed with new engine last spring.

My question could alternator be malfunctioning, I think I’ll take to get tested. And Can I or should I put a larger alternator in it. What is the amprage of stock alternator? How high amps is recommended.


1968 4 dr Impala
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post #2 of 5 (permalink) Old 02-17-2019, 02:27 PM
Join Date: Jan 2006
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Lot to go wrong here if you get the wrong parts. A Delco SI alternator is the most common in a parts house because it was used from 1973 up until the CS (aka one wire) alternator was introduced in 1994. A 10 SI is rated at 63 Amps and a 12 SI outputs either 78 or 94 amps. It bolts in place of an older DN series, but is wired differently since it's regulator is inside the case (you by-pass the old external regulator).

You can identify a SI from the earlier DN series by the transistorized internal regulator. The CS has a solid disc in the front of the alternator to prevent air from being blown in and it has it's fan internal to the case visible in the back of the alternator. Your car should have a DN alternator used from 1963 through 1972. DN alternators were rated from 36, to 63 Amps but their out put was limited at low RPM (why your lights dim at idle,but brighten as RPM picks up).

Look at your alternator to determine what you have based upon the description provided. If you can see a transistor cooling finned heat sink in the back your parts store sold you the wrong part. As you can see a SI bolts in place of a DN as they share the same dimensions and mounting system. SI alternators are all the same except for internal parts (difference between the 10 and the 12 series) and where the charging wires enter the case (clocking)

Depending upon where you mount the alternator the two prongs for the white and blue wires should be easy to get to. If not you have to take it apart and rotate the where the charging port is located (involves holding the brushes up with a tooth pick).

Finally your alternator should be marked with a model number and a rated out put.

You can check to see what you have in terms of an SI here. Same board has info on DN and CS alternators as well.

Big Dave
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post #3 of 5 (permalink) Old 02-18-2019, 09:52 AM
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Join Date: Jan 2018
Location: Coopersville, MI
Posts: 261
If your not doing a numbers show car or all original restoration now would be a good time to go to a single wire alternator conversion. It really simplifies everything and they are more efficient than the older style.
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post #4 of 5 (permalink) Old 02-18-2019, 05:56 PM Thread Starter
Join Date: Nov 2017
Location: SE PA
Posts: 28
Well it looks like I have a 61 amp external regulated alternator. Auto zone part number DL 7122. I think I’ll pull it and have it checked/replaced as it has lifetime warranty.

Thanks guys for the info!


1968 4 dr Impala
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post #5 of 5 (permalink) Old 02-18-2019, 10:39 PM
Join Date: Feb 2019
Posts: 59
If its a reman its a good chance that it could have failed. I just did the one wire conversion and its a lot better. I went from a 35 amp to a 105 amp brand new powermaster for $115 from summit. World of difference and ready for the extras.
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