I have a 2000 C5 Corvette with 200,000 miles on it.
My gauge for my volts read 0.7 and my battery was bad. I replaced my battery and it did not fix it. I also replaced the Alternator and it did not fix the issue. My car is acting like the Alternator doesn't exist. It will not charge my battery at all. If i disconnect battery with the car on the car will shut off immediately. I need help I have no idea as what this could be. I ha e checked the grounds and the fusable link at the starter. I even cleaned the connectors on the PCM. My car still reads .07 volts on the gauges and a message pops up on the DID system charge fault. Please help this is my daily!!!! Thank you for any advice or knowledge!

 

I had the aftermarket duralast, its the autozone brand. I just removed it and taking it back tomorrow for refund. When i put the original one in it still says the same thing and voltage on the cluster gauge is at 0.7 volts. Tomorrow I will check the voltage with a volt meter. Is it possible the PCM is out on my car. I don't have any check engine light on itand the car won't let me run a diagnostic on it through the DIC. Like what else could cause this. I am going to find someone to rebuild my old one tomorrow, but it just seems like something else is missing on the charging circuit. I feel with the new alternator it should have at least charged the battery somewhat. It just acts like nothing is there also when i would disconnect battery the car would just shut off. Shouldn't it of stayed on with the new alternator. Or are corvettes really that picky with their alternators? Its just the most bizarre problem i have ran into.

 

I just checked the Alternator when engine is running it shows 12.1 volts. Also at the battery terminal it will show the same 12.1 volts. Took my original alternator to an auto electric shop and they said my alternator tested good. So idk if somewhere there is a bad ground. When the car is in the on position with engine not running the alternator and battery both test at 12.3. With the lights on the volts go as low as 11.97-12.07 at alternator and battery. Please and thank you for all the help!

 

The volts for alternator and battery with car on with engine running are 12.3 volts. With the lights on while engine running volts are 11.87-12.1 volts. When the car is on with engine not running the volts are 12.3-12.47. Also i took my original alternaor to an auto electric shop and they said my alternator tested good. I put it back in and the system charge fault went away but it still has low voltage on the DID display and gauge reads 0.7 volts still. Also service vehicle soon pops up now, but i still have no check engine light on. Please and thank you for all your help, i am clueless on this problem.

 

If the battery and the alternator large lug read the same, that wire is good. If the engine ground is bad, or you have no field reference voltage at the small plug, it will not charge.
I would try making a small jumper wire and clipping on the battery lead, and put it momentarily on the field wire. If it acts like it is loading the engine, you have no field reference, so the alternator stops charging.
I do not have a wire schematic for that alternator circuit, so someone with a wire print will have to help out.
you are going to need the wire routing from when the key goes to on, and the fusible links, and the ground paths.
I think your alternator popped the fuse or link somewhere, and you just have to hunt it down.

I got a rebuilt alternator for my daughter's honda from autozone, and the alternator went to 19 volts, and I tried ldiagnosing it from the phone, and it turned out to be a bad regulator internally.
Since you had yours tested, that's not it, but be aware that low volts can happen, just as high volts can happen as well.
I would check the output of the ignition switch, since it is the one thing that always gets used every time you drive the car that is an electrical component.
Pull the right floor panel, and check for fuses. turn the key on, and see if there is any volts on any of the terminals on the small plug at the alternator.

 

Here is the schematic for the charging system :

 

In the diagram above, there is a fusible link on the alternator field wire.
If that is not a good fusible link, the alternator will not charge.
We already know that the fusible link to the left of it is good, because battery voltage is present at the alternator. You need to remove the alternator connector, and check for voltage at wire D.
Right in the middle at the top of the diagram, there is a fuse for the voltmeter, it is just below the label "hot in run and start" it is labelled minifuse, 10 amp.
That means that that wire is powered when the key is in positions run and start, the wire has volts. I would check that fuse, since the voltmeter has no volts to sense.Check those two items, and I think your problem will go away if you have to replace both or just one.
The voltmeter should tell you what the volts are before you start the car, indicating battery condition prior to a start sequence.
The voltmeter is also powered during a start to give you the condition of the battery during a start.
It is not uncommon for the battery to go to 10 volts on start initially, but half a second later, it should indicate at least 11.5 volts in the middle of the start.
It happens fast because the fuel system is already precharged with residual fuel pressure, since the check valve in the fuel pumps is holding line pressure with the engine off. If any of the injectors leak, your pump would run to prime the manifold, then shut off. then it will run again to supply run fuel. If the injectors leak, or the check valves are bad, the start takes longer, and leaves you wondering .... Why did that take so long?

 

I'm curious where that diagram came from because it implies the voltmeter gets it's voltage from the serial bus.

The real GM service manual specifically states the IPC reads the voltage directly from the ignition 1 circuit. It then drives the voltmeter and displays that voltage in the DIC. The power source is fuse 19 in the footwell fuse box.

Since your voltage is apparently reading 0.7V on the cluster with the engine running you really need to check the voltage on both sides of fuse 19. You may have an ignition switch problem or a power distribution problem. It just so happens that the same switched ignition source that powers the footwell fuse 19 for the cluster also powers the underhood fuse 16 for the PCM. If you're not getting the correct switched ignition voltage to the IPC the voltmeter won't show the correct voltage and if you're not getting the correct voltage to the PCM then the alternator might not work.

 

Ok i checked the field wire in the Alternator connector which i believe is the grey wire. That cam back with 0.0 volts reading. The wire labeled with S, which is a red wire tested at 12.5 volts. The other wire labeled L, was another red wire and that tested at 10.1 volts. So the problem would be the fusable link connected to starter it sounds like. I hope this fixes it thank you'll for the help the car has been out for two weeks because of this problem

 

S is the wire with the fusible link and it tested OK.

The field wire would be 0V when not running.

 

So S is the wire that connects to both fusible links at the starter?

 

S is pin D of the connector and is the "1 RED" wire with the "0.5 GREY" fusible link in the diagram.

It does not connect to both fusible links at the solenoid, just one. The wire on the big stud on the back of the alternator connects to the other fusible link.

 

I remember the good old days of red wire from Alt to batt and all is well !!!!!!!!!!!!!!! I wonder why it needs to be so complicated ????( I kinda know the answer)

 

Ok so took a picture of what I checked the voltage on. Not sure if it was the right way to look for charging problem.


I placed connector so the letter labeling will match up with metal contact. On the right side is metal contact S, the voltage on that read 12.3-12.5 volts sometimes as low as 11.3 volts depending on how well the battery is charged. The metal contact labeled F, in the middle has a voltage reading between 0.1-0.3 volts. The metal contact labeled L, to the left has a voltage reading between 10.1-10.3 volts. The test was performed with the car on and engine running. Is that the proper reading?

 

On the alternate connector it has SFL, labeled for metal contacts in plug. What is the voltage suppose to be for them? On S that read 12.3 volts it fluctuates depending on how charged battery is. The F metal contact read 0.1-0.3 volts. The L metal contact read 10.1-10.3 volts. Is that where i was suppose to check them at? I also checked them with engine running.

 

The connector is A-B-C-D left to right as you hold it. And yes, the voltages you measured are correct.

The engine running or not doesn't matter because you disconnected the connector. Key on or key off is all that matters.

 

What ever happened with your car? Having the same exact issue with my car.

 

You should try to send him an e-mail. He hasn't been on since 10-22.

 

Im also having the exact same problem. New alternator, new battery, new starter. Wont charge. If anyone has this issue solved, let me know.

 

These cars are very picky on the alternator. I went through a few of them before I tracked down an oem rebuilt off of the exact year of my car. Put it on and worked like a charm. I even bought an extra off a crashed low milage one just in case it ever happens again.