DocSki808

Hello everyone,

I own a 2006 C6, which has been having some alternator issues for a while now and I am at a loss for what could be causing it. Also, I am currently located in Germany, and just went through a winter here with her, yes she still ran during winter as far as minor drives to keep her going, no issues during the main months of that. Here is a rough repair timeline I have done for my car up to this point to try and diagnose the issue.

1st Issue:
Car is having issues starting and staying above 11v-11.5v (standard battery)
- Replaced Alternator from high output to an Original Duralast Alternator
- Replaced Starter
- Replaced Battery to d34 Yellow top (installed in backwards due to pos/neg being on opposite sides for this one.)

Everything worked great after this was fixed for roughly 4-5 months.

Next issue:
After fueling up one morning around 9 am the car was sitting at 13.5v as usual. Come lunch time around 11:30 when I started the car, it was instantly down to 11.5v.
- Put a charger on the battery rest of day into the night, removed around 10pm that night. When removed the battery was at 13.5v. Come morning, go to start her up and back to 11.5v.
- Put charger on her again, same issue, back down to 11.0-11.5. Driving her she will get up to maybe around 12.0 then drop back down to 11v-11.5v.


I am currently at a loss as to what could be causing the issue. There is no aftermarket sound system in the vehicle. All current work done on her is COMP CAMS, headers, the exhaust, internals and she has a deep loping idle.

Here is what else I have done to diagnose issue.

- Tried installing additional ground cables (4ga) off of the battery (2 additional, upgraded the old one) just in case battery wasn't properly grounded).
- cleaned off all grounds I could find, replaced battery cable terminals.
- removed the ONSTAR fuse.
- cleaned the throttle plate of all carbon deposite.
- had an alternator test done on it by auto store, battery is still good, alternator is charging at only 12.06v.

- conducted a voltage drop test with these results
- alternator housing to negative battery terminal = 0.00v
- alternator bracket to negative battery terminal = 0.00v
- alternator B+ bolt to positive battery terminal =3.73v
- alternator housing to positive battery terminal = 11.73v
- negative terminal to engine bolt = -0.01 to -0.03

With car off after car charger used to charge to 12v (generic car charger) -

Battery at 12.10v car off and holding down accessory button for 10 sec mode w/headlights on
- 12.19v headlights off

Car on
Headlights off - 12.01
Headlights on - 11.93
- stereo on - 11.93
- heater on - 11.89
- seat warmers - 11.84

All was measured using a multimeter, during this time DIC was reading
11.8 at car on
11.6 with all accessories on
11.3 at end of all testing (20-30 minutes running)

I did notice that part way through testing with all accessories on, car sounded like it was about to die or struggling to stay running, when I turned off accessories it returned to normal, then did it again a little later with no accessories running, I want to chalk this up to it just being low battery but not sure. It doesn't make sense that my car should be eating alternators this often like this, any ideas would be greatly appreciated.

LMB-Z

Do you keep the battery on a battery tender? It might not be eating alternators, just not keeping the battery with a good charge everyday.

Cooter Tech

How often do you drive it and what distances? You might not be driving it long enough to get the battery fully charged. Is that the voltage output from alternator when car is running, if do it is too los. Is the alternator belt in good condition and tight? Are all your lights turning off (time delay working properly). Interior lights turning off. Glove box light, trunk light etc.

Icecap

What is the Voltage at the Alternator + terminal to ground or the Alternator housing when the engine is running and no accessory load?

A fully charged battery should read 13.6 Volts (2.2 Volts per cell) If the Alternator can't deliver more than 14 Volts it isn't charging properly since it takes that to overcome the internal resistance of the battery.

Garry in AZ

Alternator output terminal to battery positive should not have anywhere near 3.7 volts of drop. With the car at an idle, this number should be less than 1 volt. If you are loosing 3.7 volts of alternator output, your battery will never see more than 11 volts. That's not gonna charge it!
Check the alternator output wire from the alternator to the starter terminal to the fuse box. Find out where the drop is coming from, and you'll have solved your problem.
Best of luck with it.
Garry

DocSki808

It sits on a battery charger all night to keep it up. Not a tender but a charger.

Drives roughly 2 miles to work and back about 6 times a day when I take her. The last time I took her roughly 40 miles out and 40 back battery went from 12.0v at start on DIC, to barely making it home as all electronics started turning off enroute, i.e. Stereo, handling, etc. when I hit driveway I was below 8.0v.

Voltage for alternator + terminal to ground is -0.00

I will check that wire going to starter today and post an update on this forum, thanks for all insight everyone.

KEZ06

On mine I had a wire come loose on the stator so when it spun the wire touched inside the alternator and caused voltage drop at 2000 rpms. At
Lower rpms it charged fine. Had the slternator rebuilt. No prob. Since.

AORoads

I didn't think you could keep the batt. on an actual charger all night for many nights without cooking the batt. too much. Have you done a load test on the batt.'s cells to see if they are holding a charge?

Cooter Tech

Sounds like a defective alternator, it is not keeping up with the demands of the car.

If you are using a battery charger and not a battery tender, I think over a period of time a charger will ruin a battery. I can't prove it, but that has been my experience

bassman50

From what you describe, it sounds as though you have a defective alternator. You should be seeing an output from the alternator (at the output wire's connection point on the back of the alternator) of about 14.2 - 14.5 volts at about 2000 RPM. If you have a bad diode, the alternator will charge, but not enough. . . .and the bad diode, if it's leaking, will discharge the battery.

As Cooter Tech mentioned, get yourself a battery tender - - it will maintain a battery without overcharging it, whereas a charger, even in trickle mode, may eventually ruin a battery. Also, most chargers will shut off when the proper battery voltage is reached; a tender will keep providing a voltage to the battery.

Steve

irok

what brand of spark plugs are you using?some on here have charging issues if using NGK plugs.try the factory plugs.lot of problems reported with yellow top batteries here on the forum also

rkj427

read this old topic.....................

https://www.corvetteforum.com/forums...-question.html

check the following items from this posting...................

With a multimeter in hand set to 20v DC,

Start the car with the hood open.

Put the ground probe of the multimeter to the body of the alternator, and on the back of the alternator under the rubber boot, put the positive probe to the threaded part of the terminal (not to the cable part). You should have 14.6 volts if the alternator is good.

Now put the probes to the battery lead terminals and check voltage. The voltage should be 14.5 volts (about .1 voltage less than the alternator direct reading since you will loose this small voltage in the wiring/motor aluminum between the positive and negative paths between the two).

In the car, kick the DIC over to voltage, and the reading should be about .3 volts less than the battery reading (again, loss from the wiring/devices from the battery to the gauge cluster and if the altinator is putting out 14.6, then the DCI should be reading 14.2~14.3 .

So if you have 14.6 at the alternator terminal to the alternator body direct, but the voltage is dropping way down after that, it not a alternator problem, but a wiring connection problem instead.

The positive red cable off the back of the alternator terminal bolts to the starter on one terminal, goes through a bond bar in the starter, then to another red wire that goes back up to the battery, the a smaller red wire that goes the fuse block terminal.

On the ground side, the large negative black wire bolts to the engine block just above the starter, and another black negative wire bolts to the chassis just below the battery.

So all these wires, and there connection need to be pulled, the wire connectors cleaned, the bolting terminals cleaned, then use dielectric grease on the connecting parts before reinstalling the wires to slow them down from corroding/oxidizing again.

And as stupid as it may sound, I have seen problem of even just a bad connection from the back of the alternator terminal to the first wiring contact that has caused low voltage problems.

Note, if your DIC is reading 14.6 at idle, then the alternator is pushing at least 15.1 volts at idle to the battery instead. I bring this up, since if you are pushing more than 15.1 volts to the battery (say at mid revs and higher), then you are over voltage's the battery when it's being charged, and will shorten the life of the battery instead as you are boiling it. I bring this up for the guys that state that their DIC are holding fast at 14.6V, and may want to pull voltage on the battery when the engine is rev'd up to make sure that the battery is not getting more than 15.1 volts at any given time.

CadVette

I once made the mistake of buying a Duralast alternator. Only lasted about a year before it failed. They have cheap Chinese internal parts. You can buy quality a rebuild kit and do it yourself or find a local shop that rebuilds alternators. Buying an original GM alternator is an option also. With the engine running you should see over 14 volts. If you believe something is pulling the battery down use the ammeter section of your multimeter and monitor current draw in series. Pull one fuse at a time until you find the offending circuit.

rkj427

GM alternators can be purchased on Amazon...................... less money than dealerships

DocSki808

Thank you all for all of this information,

Here is what else I have done to diagnose since last post,

- car started to have issue starting and finally wouldn't start, turns out while tracing last wire from alternator to starter it had been corroded and detached. Replaced it with a 4g wire and started back up normally, seems to hold a better charge now, but still having issues charging.

- conducted a voltage drop test with these results
- alternator housing to negative battery terminal = 0.00v
- alternator bracket to negative battery terminal = 0.00v
- alternator B+ bolt to positive battery terminal = 0.00v
- alternator housing to positive battery terminal = 12.01
- negative terminal to engine bolt = 0.00

With car off after car charger used to charge to 12v (generic car charger) -

I did notice that part way through testing with defrosters drops to 11.4v, with seat warmers drivers and passengers, stereo, heater all on, car idle drops from 800-500 and struggles to remain on if left to idle, it returns to normal after all are turned off.

I will continue to try more of these options you have all given me and get an alternator test run tomorrow to see if what I have done has improved it at all. I will also disconnect all of those leads and apply that grease thanks!

unixcorn

"Drives roughly 2 miles to work and back about 6 times a day when I take her. The last time I took her roughly 40 miles out and 40 back battery went from 12.0v at start on DIC, to barely making it home as all electronics started turning off enroute, i.e. Stereo, handling, etc. when I hit driveway I was below 8.0v."

Even if you did fix the issue with the corroded wire at the alternator, 12 starts (2 miles to work and back 6 times a day) with only 24 miles driven will not recharge the battery enough to recover from the starts. I think you need a high performance alternator to take up the slack. Just my opnion. Please keep us posted.

guitarman715

Its the duralast alternator, I just went through 3 of those piece of junks since January. The 3rd one was bad right out of the box! It wouldn't charge past 13.5 and the service charging system light came on constantly. I took mine back to Autozone and switched it out for a remaned AC Delco unit, and I have had no problems since, it charges 14.2-14.5, only occasionally dropping lower. I would get rid of the duracrap first and then see where you stand.