Alternator Differences
Thread Starter
Running Guns & Moonshine
Joined: Aug 2001
Posts: 12,650
Likes: 7,292
From: CT
Alternator Differences
What are the differences among alternators between the C5 production years? Why would we be unable to swap one for another?
I know some had clutches, others did not. Which is best for a. Supercharged car?
Are C6 or C7 alternators viable?
I know some had clutches, others did not. Which is best for a. Supercharged car?
Are C6 or C7 alternators viable?
Safety Car
Joined: Mar 2017
Posts: 3,770
Likes: 940
From: Orlando Florida
On the top of the c5-tech forum page are a listing of stickies -- sub-forums that are always in view -- one of which is exactly what you are looking for:
https://www.corvetteforum.com/forums...nd-issues.html
From the looks of it, for a 99 you'll have to have an early style alternator, or live with a charge fault, and the early style don't come from the factory with a clutch hub, though it might be able to be retrofitted with one.
https://www.corvetteforum.com/forums...nd-issues.html
From the looks of it, for a 99 you'll have to have an early style alternator, or live with a charge fault, and the early style don't come from the factory with a clutch hub, though it might be able to be retrofitted with one.
Last edited by redzg; Mar 15, 2020 at 05:49 PM.
Melting Slicks
Joined: Jan 2009
Posts: 3,275
Likes: 739
From: Miami FL
What makes the C5 alternator so peculiar is that it is excited when its regulator receives a turn on signal of 10v at limited current provided by the PCM through the L wire. Not all regulators accept the turn on signal provided by the C5 PCM.
Another distinctive attribute described by Lionelhutz in this post:
The stock alternator has a soft turn-on regulator. You can watch how slowly the voltage increases when the engine starts. So, I suspect the message is caused by some aftermarket units that do not have a soft-start and basically jump to a high duty cycle until the voltage rises and the duty cycle drops again. The PCM is seeing the duty cycle go too high which triggers the charge fault message in the DIC.
Last edited by GCG; Mar 16, 2020 at 01:56 AM.
Racer
Joined: Dec 2017
Posts: 331
Likes: 74
From: Florida
Yes the C5s have very specific voltage regulator circuits. On this schematic I count 6 diodes, 2 transistors, 2 resistors, and 1 capacitor.
1997-2000: The manuals and autos did not have clutches, all 110 amp.
2001 (roughly around this year): The autos had clutches in the pulleys, and manuals remained clutch-less, all 110 amp.
Mid 2003: The amperage changed from 110 to 145 for both manuals and autos which affects the way the regulator is built, and what the PCM sees.
These above dates are rough estimates and if you have the original alternator, you can look at the part number and cross reference it. Or if you have access to the build sheet, it might tell you.
I've had a lot of alternator woes, and I wouldn't recommend using anything other than what your specific transmission and year used, even supercharged. I'd also go for a Valeo OEM unit, or rebuilding the voltage regulator if the windings aren't completely shot. A lot of aftermarket brands don't get these correct.
1997-2000: The manuals and autos did not have clutches, all 110 amp.
2001 (roughly around this year): The autos had clutches in the pulleys, and manuals remained clutch-less, all 110 amp.
Mid 2003: The amperage changed from 110 to 145 for both manuals and autos which affects the way the regulator is built, and what the PCM sees.
These above dates are rough estimates and if you have the original alternator, you can look at the part number and cross reference it. Or if you have access to the build sheet, it might tell you.
I've had a lot of alternator woes, and I wouldn't recommend using anything other than what your specific transmission and year used, even supercharged. I'd also go for a Valeo OEM unit, or rebuilding the voltage regulator if the windings aren't completely shot. A lot of aftermarket brands don't get these correct.
Last edited by 02torchred; Mar 16, 2020 at 02:15 AM.
Melting Slicks
Joined: Sep 2007
Posts: 2,138
Likes: 139
From: Port St Lucie Florida
Your gonna get alot of answers saying how specific the valero alternator is to the C5, which may be true. But I was tired of going thru batteries because of the low voltage output of the original alternator. I did everything they said on this site regarding checking ignition switch and so on, starter solinoid wires etc.
I just bought an autozone alternator supposed to be specific to the C5 the 110 amp automatic and it upped my voltage increase to .5 more volts.
I do get the charge system fault, but it still charges the battery, no problem, the car still drives great, all I am gettin is a message on the DIC, I think I can live with that, instead of being stranded or broke down somewhere because of an weak battery from a factory alternator. GM really missed this one. Oh my car is supercharged over 600 hp and I am running a lawn tractor battery from walmart. To save weight. I posted pictures of it on one of my posts.
I just bought an autozone alternator supposed to be specific to the C5 the 110 amp automatic and it upped my voltage increase to .5 more volts.
I do get the charge system fault, but it still charges the battery, no problem, the car still drives great, all I am gettin is a message on the DIC, I think I can live with that, instead of being stranded or broke down somewhere because of an weak battery from a factory alternator. GM really missed this one. Oh my car is supercharged over 600 hp and I am running a lawn tractor battery from walmart. To save weight. I posted pictures of it on one of my posts.
Last edited by corvet786c; Mar 16, 2020 at 04:42 AM.
Racer
Joined: Dec 2017
Posts: 331
Likes: 74
From: Florida
You've probably added 80+ lbs with the supercharger kit, which is right on the nose of the car. The lawn tractor battery you're using to save weight is probably only a 12 lb difference max. Having about half the cold cranking amps as stock, it probably won't last long, and is probably more or less the reason for your CHARGE SYSTEM FAULT message rather than the alternator. Batteries can act as a current ripple smoother, as well as tieing into other factors that complete the charging assembly.
Last edited by 02torchred; Mar 16, 2020 at 02:47 PM.
Melting Slicks
Joined: Jan 2009
Posts: 3,275
Likes: 739
From: Miami FL
You've probably added 80+ lbs with the supercharger kit, which is right on the nose of the car. The lawn tractor battery you're using to save weight is probably only a 12 lb difference max. Having about half the cold cranking amps as stock, it probably won't last long, and is probably more or less the reason for your CHARGE SYSTEM FAULT message rather than the alternator. Batteries can act as a current ripple smoother, as well as tieing into other factors that complete the charging assembly.
The original problem was an abnormally high voltage drop in the alternator-starter-battery chain: almost 1V. Click here to check Post 5 of his thread for more details.
As a result of that, voltage at battery was 13.5V, but even though voltage at alternator was not disclosed, it was calculated as being above 14.2V
(Click here to check Post 7 of his thread for more details).The real solution would have been to fix the original problem, not find an alternator with an output of almost 15V to compensate for the voltage drop. Needless to say that such a high output is kind of dangerous...
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Melting Slicks
Joined: Sep 2007
Posts: 2,138
Likes: 139
From: Port St Lucie Florida
The fact is that he changed the alternator for the wrong reason and now is spreading misinformation in 3 different threads.
The original problem was an abnormally high voltage drop in the alternator-starter-battery chain: almost 1V. Click here to check Post 5 of his thread for more details.
As a result of that, voltage at battery was 13.5V, but even though voltage at alternator was not disclosed, it was calculated as being above 14.2V (Click here to check Post 7 of his thread for more details).
The real solution would have been to fix the original problem, not find an alternator with an output of almost 15V to compensate for the voltage drop. Needless to say that such a high output is kind of dangerous...
The original problem was an abnormally high voltage drop in the alternator-starter-battery chain: almost 1V. Click here to check Post 5 of his thread for more details.
As a result of that, voltage at battery was 13.5V, but even though voltage at alternator was not disclosed, it was calculated as being above 14.2V
(Click here to check Post 7 of his thread for more details).The real solution would have been to fix the original problem, not find an alternator with an output of almost 15V to compensate for the voltage drop. Needless to say that such a high output is kind of dangerous...
If I can't share my experience and others get offended, maybe this site is not for me.
Last edited by corvet786c; Mar 16, 2020 at 06:11 PM.
Melting Slicks
Joined: Sep 2007
Posts: 2,138
Likes: 139
From: Port St Lucie Florida
ahhh, that's your opinion, whats your question? You mean about the weak Valero alternator killing batteries, the wires are fine.
Race Director
Joined: Apr 2007
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From: South Western Ontario