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Help! 2007 Corvette charging issues and not the normal stuff.. Tech question


Motor head!!!!
Feb 13, 2001
Valencia, CA,USA
88 Convert ( SOLD ) /1973 coupe 4 speed/1964 Vert!
Hi Mike here, Long time member but a C6 noob poster.
Ive been doing a fair amount of searching and coming up with.. odd info, that I'm not sure I can trust.

Vert , Auto, base 37K on chassis

The issues is No Charge aka Service charging system DIC alert.

Bit of history, Theft recovery car, engine & seats missing, E bay auction won in mid 2016.

We went through EVERYTHING and the car was up and running last Oct, passed all inspections and has been a dreamboat.

Note new Batt, starter & all harnesses under hood replaced with SUPER CLEAN OE wrecking yard stuff.

Mistake #1 bought an auto zone rebuild lasted 2 weeks, went Over voltage 2X but a shut down and restart would clear the issue.
exchanged it, 2 weeks later same deal.

Went with another manufacture 3 days later POOF, every time the alt was changed, the battery was over 12 volts and did not labor on crank

Really needed my car & went to O' reallys......plopped theirs in and NUTTIN. ( which is where we are " currently " at ) .

Last night I whipped out the FSM & ports scope.
Pin D " S" Red /White +12 from batt via horn fuse is OK and horns work.

Pin C " F " Green /Yel Pcm pulses from ECM at IDLE I have ~ 200hz 50% duty and that looks good.

BUT the ( Or/ Green ) on the schemo pin B is ECU the generator turn on signal. With the connect off / car off key on I get 5 volts DC and when I start the car it goes low.. is this correct ?

This AM [FONT=SF Optimized, system-ui, -apple-system, BlinkMacSystemFont, .SFNSText-Regular, sans-serif]did a voltage drop test from BAT to alt output. POINT 001 volt drop & measured resistance from Bat post to alt output wire .2 ohm so that's all good. No Hi resistance at the starter lug.[/FONT]

[FONT=SF Optimized, system-ui, -apple-system, BlinkMacSystemFont, .SFNSText-Regular, sans-serif]the ALT input pins look clean on the connector side.[/FONT]

[FONT=SF Optimized, system-ui, -apple-system, BlinkMacSystemFont, .SFNSText-Regular, sans-serif]My gut hunch is these are ALL POS rebuilds, but being a retired engineer.. I cannot prove it since I'm not 100% sure of pin B's actual function...[/FONT]

[FONT=SF Optimized, system-ui, -apple-system, BlinkMacSystemFont, .SFNSText-Regular, sans-serif]Going to O really's this AM to have their alt bench tested, BUT they are not sure they can test a PWM ( computer controlled ) ALT LOL ![/FONT]

[FONT=SF Optimized, system-ui, -apple-system, BlinkMacSystemFont, .SFNSText-Regular, sans-serif]Thought's ?[/FONT]
[FONT=SF Optimized, system-ui, -apple-system, BlinkMacSystemFont, .SFNSText-Regular, sans-serif]HELP ?


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I'm hoping one of our resident experts chimes in here soon to give you some help. Wish I had some advice worth giving, but alas, I am not in a position to give any. Hang tough and someone will be around soon.
You need the correct alt for the vehicle, the PCM will throw a fault code if it does recognize the correct alternator including amperage output for the coding in the PCM. You basically need a PCM and alternator that match each other.
More Alt charging info

We went to O reallys and tested my OLD alt from my trusted rebuilder...
The NEW alt worked , but we exchanged it there was something rattling in the pulley AND we tested the New Exchange one , that worked.
My OLD alt worked as well... Hmmmmmmm

When I started talking tech with them, they had nuttin.
And I still do not know "L" on pin B (Or Green ) does function wise...

So here is my next move... run a large gauge wire from the Bat out of the alt to the Bat + bypassing the starter wiring loop..

The old alt worked great, for as long as it did.
It is the " correct " ( as far as that goes ) for my car.
" the PCM will throw a fault code if it does recognize the correct alternator including amperage output for the coding in the PCM. "
So what you are saying I only get a dealer alt ???

The ONLY data ( so far ) that I could find is the Z-06 . Auto & 6 speed all use this:
6-Speed Automatic Transmission 6L80 General Motors Transmission 6 Automatic110 AMP GENERATOR(K63)

and I think it only monitors voltage to set the Charging system fault DIC message.
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And more.....

Well the O really's alt lived long enough to do the following tests.
Charged the batt back to 12 .2 volts
I ran a 8 ga wire from the BAT + to ALT +
I put everything back together & started her up. The AC was running.
Alt was putting out 14.7 at the stud.The DIC said 14.3
and I got the nice ZZZZZZZZZZZZZZZZZZZZ that the alt was charging
SO all the Alt inputs are correct, and got 1/2 volt drop from Batt + to Alt stud
Removing the 8 ga I got a 2.25 volt drop, so something is fishy.
and just a few seconds later I smelled something BAD. The O Realy's alt was SUPER HOT.
I shut down the engine, let the alt cool, pu the 8 ga jumper back on.. but ALAS it was to late
It did 14.1 and made the charging noise for about 10 sec and died. (

So I need to give this a think....
Oh and I was WRONG about the starter being new we used the one that came with the 93K engine.
So I might have a case of Starter stud itis. I'll do a new starter just cause 96K now ( engine )

I have a memory that the auto's needed a 140A alt... but I'm not 100% on that.

I think at minimum, Started & Alt.. and we go from there...
If you have the OEM PCM that was installed in your vehicle when new from the factory, then go to your local GM dealer, give them your vin number and they will pull you up the correct part number alternator for your vehicle. Yes, I would buy the correct AC Delco alternator for the vehicle if it were mine, but only if my original alternator was gone. My first choice would always be to fix the OEM alternator if you still have it.
OEM alt

That one was a core in Oct of 16 ( kicking myself ) calling dealer today to get part #'s & prices
The PCM & ECM are OE

Call the paramedics !

Local dealer:
Starter AC Delco re man 542.88
Alt AC Delco re man 724.68 (25888970) PN #

There was no service advisor to quote labor BUT if they install it LIFETIME WARRANTY !
BTW the dealership NEVER called me back AFTER 3 attempts to speak to the service dept !
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You also could get the correct replacement alternator from Rockauto.com. Its an ACD 25888970 which fits only C6 Corvette. It's on this web page and runs a little over 300 bucks.

If I was replacing the alternator on my C6, that's the one I'd get.
Thanks Hib !

I'm still trying to suss out the starter situation I have a similar price on Amazon & my GF gets FREE 2 day shipping

Corvette charging system fixed after a 3 round fight... the good news it only cost 40 bucks and that was just for a Thank you to David ( My son for crawling under the car ) !
Short answer , starter stud's nut clamping the BATT & ALT cable was LOOSE !
Tighten that up, took the O Reallys Alt out ( which had a nice charbroil smell ) and put the BNR ( rebuilder in Van Nuys Ca ) back in and we are GOLD again !
Look for the simple things first. Why don't we tend to follow this mantra? Life would be so much easier, wouldn't it? I'm so glad that you figured out the problem, and you shared the fix with us.
The thing that fooled me....

There was an internal tooth lockwasher at the back of the stud that had chewed into the lug for the batt.
And do to the thickness of the Batt cable, here was enough pressure to keep the Batt to starter solid enough so my starts were smooth..
BUT there was obvious heat issues on the Alt to Starter stud. It touch LIGHT finger pressure to move that lug.

The good news is the solenoid back didn't overheat and start cracking.....

Yesterdays voltage drop tests made that clear.

I ASSUMED that I was just a victim of crappy rebuilds.

My Local Autozone could not test their Alt's so they just exchanged, we danced that dance 2X before I got a refund.
I hind sight I just pay attention to the weather and how hot it was outside....

So use the AC more load, more expansion of the copper stud, worse connection, bigger voltage drop BAM Alt failure ( or so it seemed )...

The BNR rebuild was a Valeio ( SP? ) Original ACDelco markings, they admit Most of the time,clean up, check diodes, keep factory regulator replace brushes and bearings, and off it goes for 150.00

That one worked for a week,but failed on a cold start.. and in the driveway it went.. the BNR came out.

The first O'Really's didn't work.. in my car at all.. AND the clutch pulley seemed stiff and when you tipped it from end to end it rattled!
I had them order a replacment... but that night It was bugging me that it wasn't adding up... and there was a secondary issue.

When I went back to pick up my replacement I had my old one & the BNR... both of those AND the new exchange tested OK !

I knew then, it was just not the ALT.. the rest of the story is posted......So we learn by doing !

And some time later

Everything is PERFECT STILL, Sometime electrical stuff can come & go... but this proves out to be a fix....
Now we just wait for the starter to get baked ( again ) ....Hopefully on over 20K or more miles


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