Alternator issues
Thread Starter
Instructor
Joined: Dec 2023
Posts: 166
Likes: 14
From: Chicago IL
Alternator issues
Hey guys,
so ive been making a lot of electronic related questions here. And i think i may have found a cure to a lot of my problems. Today i put a new alternator in the car(once again) i had a 3:00 alt i needed the 12:0\0 so i got alternator part number Dl7127-12M. I work at autozone so i tested it made sure it was all good when i bought it. When i installed it i turned the car on and took my multimeter on voltage settings, and put the + probe to the battery terminal and the - to the alt case. And i was actually getting less voltage than the battery had. It read about 12.4 at the alt when before i started the car the battery was 12.6. Now i have no clue why it i snot charging my car what could it be? The alternator itself is good, so why wouldnt it charge? Also hoping the reason it dont charge is the reason my headlights don’t work. Might be a bit of wishful thinking but i wanna be done with everything wiring or electronics related LMAO. So my main question why wouldnt my alternator be charging my car? What are the common causes and how do i solve them?
Thanks yall,
Air_drewdy
so ive been making a lot of electronic related questions here. And i think i may have found a cure to a lot of my problems. Today i put a new alternator in the car(once again) i had a 3:00 alt i needed the 12:0\0 so i got alternator part number Dl7127-12M. I work at autozone so i tested it made sure it was all good when i bought it. When i installed it i turned the car on and took my multimeter on voltage settings, and put the + probe to the battery terminal and the - to the alt case. And i was actually getting less voltage than the battery had. It read about 12.4 at the alt when before i started the car the battery was 12.6. Now i have no clue why it i snot charging my car what could it be? The alternator itself is good, so why wouldnt it charge? Also hoping the reason it dont charge is the reason my headlights don’t work. Might be a bit of wishful thinking but i wanna be done with everything wiring or electronics related LMAO. So my main question why wouldnt my alternator be charging my car? What are the common causes and how do i solve them?
Thanks yall,
Air_drewdy
Le Mans Master
Joined: Jan 2001
Posts: 6,713
Likes: 1,372
Air_drewdy
Your alternator should be putting out a little more than 14 vdc at the battery terminals.
Take a reading with your car idling and see what it reads. Of it does not put out at least 14 vdc at the battery terminals then you need to go retest and see what it is doing.
As far as the clocking, you can reclock 12si alternators fairly easily...but neither here nor there. That 7127 alternator is only 61 amps.
If you're buying a new alternator, and you're staying with 12si, then I would recommend the 7294-9. You can see that the output terminal is at about the 7:00 o'clock position (looking at it from behind) so the output terminal is away from the exhaust and away from the head and should work for you also.
https://www.autozone.com/batteries-s...directUrl=true
I had one of those 7294-9 before I went to the 140-amp CS-144. If you're putting in a new alternator then you might as well go to the 7294-9.
But FIRST get a voltage reading at the battery terminals with engine idling and tell us what it reads.
Your alternator should be putting out a little more than 14 vdc at the battery terminals.
Take a reading with your car idling and see what it reads. Of it does not put out at least 14 vdc at the battery terminals then you need to go retest and see what it is doing.
As far as the clocking, you can reclock 12si alternators fairly easily...but neither here nor there. That 7127 alternator is only 61 amps.
If you're buying a new alternator, and you're staying with 12si, then I would recommend the 7294-9. You can see that the output terminal is at about the 7:00 o'clock position (looking at it from behind) so the output terminal is away from the exhaust and away from the head and should work for you also.
https://www.autozone.com/batteries-s...directUrl=true
I had one of those 7294-9 before I went to the 140-amp CS-144. If you're putting in a new alternator then you might as well go to the 7294-9.
But FIRST get a voltage reading at the battery terminals with engine idling and tell us what it reads.
Thread Starter
Instructor
Joined: Dec 2023
Posts: 166
Likes: 14
From: Chicago IL
I made sure before testing that my prongs were all the way in and they were. They snapped into place albeit they are a little corroded on the connector, and those wires are old. But I believe when i tested it it had a minimum 13.3 and a max 15.2 with an average in the 14s. Ima double check again though to be sure. I did check the voltage at the battery and with the car idling it was 12.3-12.4 lower than the battery when the car is off. I’ll see if my autozone has that alt in stock when i go to work today and I’ll swap em out. What other alternators from autozone could be better? I’m fine with the one i have now my main concern is getting my battery charged no matter the alternator. What could my issue be? I’m quite stumped.
Thank yall,
Air_Drewdy
Thank yall,
Air_Drewdy
Thread Starter
Instructor
Joined: Dec 2023
Posts: 166
Likes: 14
From: Chicago IL
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Thread Starter
Instructor
Joined: Dec 2023
Posts: 166
Likes: 14
From: Chicago IL
probably a good idea especially since its easy being right behind my seat LOL. Just a quick question i realize that sometimes these tests at autozone can say pass when its a bad alternator. How many amps should this thing be putting out. What do i need to look for on the test sheet for me to truly determine the state of the alternator.
Race Director
Joined: Mar 2017
Posts: 11,923
Likes: 4,495
From: Virginia
What alternator did you buy? If you want to add electric fans in the future, you don't want a stock alternator, but you will need to upgrade wiring to match.
If you bought a stock alternator rebuilt in PRC, it mght make the 42 or 63 or whatever amps listed on the case, at 3000 RPM, or not.
If you bought a stock alternator rebuilt in PRC, it mght make the 42 or 63 or whatever amps listed on the case, at 3000 RPM, or not.
Thread Starter
Instructor
Joined: Dec 2023
Posts: 166
Likes: 14
From: Chicago IL
What alternator did you buy? If you want to add electric fans in the future, you don't want a stock alternator, but you will need to upgrade wiring to match.
If you bought a stock alternator rebuilt in PRC, it mght make the 42 or 63 or whatever amps listed on the case, at 3000 RPM, or not.
If you bought a stock alternator rebuilt in PRC, it mght make the 42 or 63 or whatever amps listed on the case, at 3000 RPM, or not.
Race Director
Joined: Mar 2017
Posts: 11,923
Likes: 4,495
From: Virginia
Many need to be "excited" before they output anything. And if the 2-spade connector is not wired properly (including inside the car), it may never work. And at 600 RPM, you may get very little, or nothing at all, through no fault of the alternator itself.
Hence the suggested test. 😀
Hence the suggested test. 😀
Le Mans Master
Joined: Jan 2001
Posts: 6,713
Likes: 1,372
Air_drewdy
I concur. Take the voltage reading with the car idling at about 750-800 rpm.... rev it up a couple of times before settling at 750 - 800 rpm for the reading.
Even if your alternator is not charging well enough at idle it will be good to find out and at that point swap it out for that 94-amp 12si..... it will all be good thing.
FYI- the original 61-63 amp alternator on my 68 (10DN I believe it was?) was just barely capable of maintaining battery terminal voltage if i drove at night with the lights on and the heater fan running.....and I didn't have any other loads back then (well radio); but really it just wasn't enough capability.
I concur. Take the voltage reading with the car idling at about 750-800 rpm.... rev it up a couple of times before settling at 750 - 800 rpm for the reading.
Even if your alternator is not charging well enough at idle it will be good to find out and at that point swap it out for that 94-amp 12si..... it will all be good thing.
FYI- the original 61-63 amp alternator on my 68 (10DN I believe it was?) was just barely capable of maintaining battery terminal voltage if i drove at night with the lights on and the heater fan running.....and I didn't have any other loads back then (well radio); but really it just wasn't enough capability.
Many need to be "excited" before they output anything. And if the 2-spade connector is not wired properly (including inside the car), it may never work. And at 600 RPM, you may get very little, or nothing at all, through no fault of the alternator itself.
Hence the suggested test. 😀
Hence the suggested test. 😀
Safety Car
Joined: May 2001
Posts: 4,747
Likes: 1,642
From: Fairfax Virginia
I bought an alternator many years ago that was a One wire style. On the car it would not start charging until the engine was revved above 800 rpm. Until you revved it the alternator would not make any output charge.
Once it was woke up the alternator would charge the battery like a normal car. If you continue to have problems then check the two Fusible Links near the starter motor. I do a continuity test thru them to verify the fusible links are okay, if they are not okay you will have problems with your alternator.
Once it was woke up the alternator would charge the battery like a normal car. If you continue to have problems then check the two Fusible Links near the starter motor. I do a continuity test thru them to verify the fusible links are okay, if they are not okay you will have problems with your alternator.
Le Mans Master
Joined: Jan 2001
Posts: 6,713
Likes: 1,372
Air_drewdy
I was actually a little surprised that they were still putting weak 61-63 amp alternators on 1979 Corvettes!??!?.
You're already doing well coming here and asking for pointers and whatnot.
I've learned to come here and ask before going off and re-inventing the wheel.
I've never had problems with the remanufactured alternators from Autozone (or any of the other big stores either) ----
I'm going to guess that your terminal voltage will be ok once you rev the engine (to excite the alternator) and take the reading at 750-800 rpm..... BUT really, since you're already at it I'd swap over to the 7294-9.
I was actually a little surprised that they were still putting weak 61-63 amp alternators on 1979 Corvettes!??!?.
You're already doing well coming here and asking for pointers and whatnot.
I've learned to come here and ask before going off and re-inventing the wheel.
I've never had problems with the remanufactured alternators from Autozone (or any of the other big stores either) ----
I'm going to guess that your terminal voltage will be ok once you rev the engine (to excite the alternator) and take the reading at 750-800 rpm..... BUT really, since you're already at it I'd swap over to the 7294-9.
Thread Starter
Instructor
Joined: Dec 2023
Posts: 166
Likes: 14
From: Chicago IL
Thank you all so much hopefully this will be my fix im gonna take it for a little ride see our battery terminal voltage. And thank you for that info about the fuseable link it’s good to know it’s that one. When i replaced the starter i had to do so repair on it. The guy who owned the car before me i **** you not connected the ends of the link together(they must have been severed) with the pigtail cap that you use when wiring a home i about lost my mind when i saw that LMAO. I took it off trimmed the wires to clean conductor but a butt on it crimped and shrink wrapped it so hopefully thats all good. I’ll look for that alternator at work today in case mine doesn’t have it though what other autozone alternators which is either valucraft or DL part numbers are better. And then my last question to do a continuity test with that link how do i go about that with my multimeter this is all quite new to me so baby terms are appreciated lMAO.
Thread Starter
Instructor
Joined: Dec 2023
Posts: 166
Likes: 14
From: Chicago IL
Air_drewdy
I was actually a little surprised that they were still putting weak 61-63 amp alternators on 1979 Corvettes!??!?.
You're already doing well coming here and asking for pointers and whatnot.
I've learned to come here and ask before going off and re-inventing the wheel.
I've never had problems with the remanufactured alternators from Autozone (or any of the other big stores either) ----
I'm going to guess that your terminal voltage will be ok once you rev the engine (to excite the alternator) and take the reading at 750-800 rpm..... BUT really, since you're already at it I'd swap over to the 7294-9.
I was actually a little surprised that they were still putting weak 61-63 amp alternators on 1979 Corvettes!??!?.
You're already doing well coming here and asking for pointers and whatnot.
I've learned to come here and ask before going off and re-inventing the wheel.
I've never had problems with the remanufactured alternators from Autozone (or any of the other big stores either) ----
I'm going to guess that your terminal voltage will be ok once you rev the engine (to excite the alternator) and take the reading at 750-800 rpm..... BUT really, since you're already at it I'd swap over to the 7294-9.
yeah i know it is kinda nuts thats like no power.
Thread Starter
Instructor
Joined: Dec 2023
Posts: 166
Likes: 14
From: Chicago IL
Quick update here. I’m at work and I got the new alternator along with a new belt just in case I get 20% off anyways so why not LOL. I did not get the valuecraft one though I got the DL one it’s the same part number same everything I just trust furs last more they have better warranty’s and I got a gold so it’s brand new too so ima slap it all in tomorrow and we pray. Thank y’all so much for all the help.
Le Mans Master
Joined: Jan 2001
Posts: 6,713
Likes: 1,372
If you get around to it - tell us what part number you got so other folks can learn from your experience.
I suggest that if you have not learned yet, then teach yourself how to solder. It is not difficult and connections are a lot more secure. Since you already use heat shrink you're halfway there. I pretty much solder most electrical connections anymore..... unless I think they may be temporary.
I suggest that if you have not learned yet, then teach yourself how to solder. It is not difficult and connections are a lot more secure. Since you already use heat shrink you're halfway there. I pretty much solder most electrical connections anymore..... unless I think they may be temporary.
Thank you all so much hopefully this will be my fix im gonna take it for a little ride see our battery terminal voltage. And thank you for that info about the fuseable link it’s good to know it’s that one. When i replaced the starter i had to do so repair on it. The guy who owned the car before me i **** you not connected the ends of the link together(they must have been severed) with the pigtail cap that you use when wiring a home i about lost my mind when i saw that LMAO. I took it off trimmed the wires to clean conductor but a butt on it crimped and shrink wrapped it so hopefully thats all good. I’ll look for that alternator at work today in case mine doesn’t have it though what other autozone alternators which is either valucraft or DL part numbers are better. And then my last question to do a continuity test with that link how do i go about that with my multimeter this is all quite new to me so baby terms are appreciated lMAO.
Race Director
Joined: Mar 2017
Posts: 11,923
Likes: 4,495
From: Virginia
Not to knock your employer, but it seems everyone gets that 20% off discount right now:
https://www.autozone.com/lp/autozone...:GEN:DIYSEASON
Check the part number at RockAuto, and you may be surprised.
And please post photos! I really hope this all works out for you.
https://www.autozone.com/lp/autozone...:GEN:DIYSEASON
Check the part number at RockAuto, and you may be surprised.
And please post photos! I really hope this all works out for you.