seems like i am being plagued by issues as of late…this new one is a battery problem, i think, but not certain…i drove around today to do a couple of errands and no problems…got home, parked it outside so i can clean out the garage a little and plastidip my track rims…a few hours goes by and i finish up so i get in my car and all i hear i click…won't start…couldnt start….didnt want to turn over….the voltage was reading around 8V on the dash…friend came over and gave me a jump start and she fired right up…so i took it to autozone to test the battery and alternator and they both pass with flying colors…

the first and obvious assumption is that i have left something on in my car that drained the battery…ive checked everything and theres nothing on…at all….what i have noticed is that while driving today, the voltage has dropped as low as 12.9V and bouncing back up to 13.0, 13.1, 13.2…as high as 13.8…ive never seen my voltage drop that low but then again i was never fixated on it either so it could just be that i am noticing it now because of the fixation of trying to figure this out…

my question is, what should the voltage be while driving, while idle? also any suggestions of what else to look for in the car to determine what this little gremlin could possibly be?

 

Put the car on a battery tender over night to fully charge/top the battery off to start with.

In the morning, pull the tender off, and measure the voltage at the battery posts with a multi meter. You should have close to 13.3 volts at the battery terminal posts. If you are below 13 volts, either your tender is not fully charging the battery, or the battery is on the way out,

Now start the car, go to the alternator, negative multimeter prob to the metal body of the alternator, positive prob to the positive wire on the back of the alternator at the wire connector under the rubber cap, check for voltage at the wire connector. Now pull the rubber cap back a little farther, and check for voltage again directly off the positive post itself. The voltage you are looking for is 14.6v either way.

Now go back to the battery with the car running, and check the battery post again. The voltage you are looking for is at least 14.5 volts with the alternator at 14.6v.




Now connect the multimeter to the fuse box positive terminal post terinal at the threads (Lift the fuse box lid to get to that terminal) , and connect the negative prob to the alternator body. The voltage you are looking for is at least 14.5 volts again (same as it was across the battery terminals.

If you have problems with voltage at the alternator, then start by pulling the alternator and cleaning it. The below link pretty much covers most of it, but when you reinstall the alternator, make sure to clean the section on the body and brackets that will mate with the mounting brackets, and use Dielectric grease on the mating surfaces (so the alternator has a good ground to the mount).

https://www.corvetteforum.com/forums...nator-fix.html


Now one you have the alternator back in the car, lets move the wire terminals.

All of the terminal ends and connecting points need to be cleaned (including the battery terminal posts) and dielectric greases as well.

So you have the positive wire off the back of the alternator connection, that wire lead down to the starter for a connection to it.

Then you have the positive wire on the other side of the starter connection, that leads back to the battery.

On the smaller positive wire off the battery terimal, you have the connector to the the fuse box in the engine bay.

On the negitive side, you have have the battery off the battery to the engine block just above the starter, and then the smaller wire to the frame ground.

Clean all the wires connectors/contact points, dielectric grease them and bolt them back in place.

As for the DCI voltage reading when you are done, it reading low about .3 volts is normal. GM went too low budget/under sized on the wires from the PCM to dash gauge, and this is way you get the slight lose in voltage reading at the dash Hence battery with car running should be at 14.5, alternator at 14.6, and the DCI claiming the voltage is 14.2'ish instead.

Now the huge kick in the nads!!!

The OEM alternator, although rated at 125amps+, only put out about 10% of that amperage when the motor is idling. So if you are stuck sitting in traffic with everything on, the battery is going to be drained down faster than the alternator can charge it back up. But with the above listed cleaning and checks, once you get the car moving again (engine rev'g past 1K), the battery will be charged up in about 5 mins instead.

 

Holy crap that's a whole lot of awesome info!!! I will try all of that and report back!! I need to buy a battery tender first so I can follow your steps. Will definitely report back. It will most likely be Tuesday as we are headed out of town shortly unfortunately.

 

I suppose a good forum search is in order but I'll ask anyway - any thoughts on a *better* alternator?

 

I have a Billet Tech. Bought it for the wrong reason, it looked cool, but it did solve my low voltage issues.

http://www.billetalternator.com/170-...odized-finish/

 

The billet tech alternator puts out a lot more amps as low rev's due to its design, but unless you have something else in the car pulling down a lot more battery power that the stock alternator can not handle (sound system with a lot of amplifiers ), the stock alternator works just fine for the stock car.

The glitch in the system, a lot of aluminum parts as conductors, and the fact that raw aluminum will oxidize barrier form pretty quickly if left bare too long. So its the oxidized bearer from age that have formed/the fresh/clean surfaces not being dielectric greased to prevent them from oxidizing in the first place, this is the real problem instead.

If you read my write up on the alternator, the improvement of it was just cleaning the contacts for the most part (the regulator to alternator body contact points being a huge one here), and then making sure to dielectric grease the contact points to prevent them from oxidizing quickly in the future instead.

To take this one step farther, have even seen a lose in voltage off the alternator from just the connector point of the positive charging wire to the terminal it was bolt to (under the back rubber cover on the back of the alternator). Hence a check on the wire connect end loop surface itself, then to the actual alternator post that the positive wire connector was bolt to, was yielding a difference of over a volt lose from just a bad connection there itself.

So to sum it up, the OEM alternator is pretty easy to pull apart to clean it and put it back together so it putting out all it has to offer like it was new (or even rebuilding it with new brushes if needed to get it back to new), and as for the main charging wires and wire contacts in the charging system, even easier to clean and grease instead.

Really, the only hard part about the wires, three of them are under the car, so you just need to jack the car up so you can get to them (two positive wires on the starter, and the negative wire to the engine block just above the starter).
Note: make sure that you have the battery disconnector before you unbolt any wires in the first place!!!


So to sum it up, I am a fan of the billet tech alternator when needed, but think that a lot of guys are upgrading to them for the wrong reason instead (throwing the baby out with the bath water, hence oxide contact problem in the OEM charging system that could be resolve via cleaning the contacts, instead of having to replace/upgrade the alternator instead).

 

Guilty!

 

I don't have anything that put a demand on my OEM charging circuit. Sound system is OEM basic single disc/radio combo.

OEM alternator is simply a marginal crappy piece of component - even after I took it apart, did everything including new brushes, silicone greased every contacts and others.......marginal improvements - it really is a waste of efforts - felt like band aid for a broken arm.

Took matter into my own hands, using selective Marine Grade components, slow and deliberately:

First these Big 3 added onto my OEM alternator:



***Not much gained using along with the OEM alternator.***

Then, these:



The sum of my efforts along with the new alternator ended up very satisfying.

Idle while exposed to more stop than go traffic - at 14.3, anything above 2500 rpm - 14.7/14.8 volts. No fluctuation.

 

quick update…car has been off since saturday night…just got back a little while ago and figured i would check voltage on the battery, 12.6v…turned the car on, started right up, checked v again, and i get 14.6-.7v…so i assume that means battery is fine and alternator is fine...

im starting to think my house is just haunted...

i'll run through a few of your tests tonight/tomorrow, dano523

 

One of the best write ups I have seen. New to C6 for me. I will take this as C6 101,
Thanks for posting.

 

Better buy a lotto ticket.

 

if you have onstar, the system has been known to discharge batteries when non-subscribed. There are threads on the subject.

just wanted to add, a battery fully charged and in good condition should read about 12.6 to 12.8 volts. The battery would have been fully charged on a Battery Tender (trade name), removed from the charging source and allowed to sit 24 hours. Most of us are not that patient. When a battery will not hold a charge, that usually means either cells have an internal short and are discharging into each other or the plates have a build up of sulphate which restricts the flow of electrons. The last condition is reversible but it takes specialized equipment to do so.

 

On my 2008, if my battery is not at least 13 volts, I have problems. Mine rides around 14.2 or so. I took the starter moter apart and cleaned it inside(not hard to do)there was a lot of dirt.. and checked all connections and that seemed to stop the no start problem Been a year now... About that time I orderd a new battery. I asked the guy to top off the charge before I came in.. He said dont worry. When installed it read about 11.9 V Guess what No start... I got my money back and I still running the old battery a year later. I would guess I need a new starter and I am not sure why it runs at 14.2 on the gauge. I do have a lot of electronics...

 

ok so voltage at the battery right now is 12.85V…voltage at the alternator is 12.85V as well…i just hooked up the battery tender and will leave it overnight and check voltage again at both sides (battery and alternator)…to be continued i suppose ...

 

Sounds like you may be ready for a new Battery of cells.... If you are driving it daily it should be at least 13 volts... Sounds like your alternater may be on the low side for a corvette. Should be in the 14 and up range.... I think it is all the electronics that are designed into it it runs a little higher than most... Im no expert but even DANO 423 said 14.6 at the ALT. Most alternators dont run that high, but the stock Corvette ALT does. These cars are so picky and often times we must comply,,,, Oh one more thing...was it 12.85 at idle??? what if you rev it up a bit????

 

Well I did this test with car off...I just wanted to get a reading before I put the battery tender on...so tomorrow I'll remove the tender, check numbers again, turn car on, check numbers again, and will post results...

 

Ok, morning test...

Battery tender on all night (it is green on the front so fully charged)

v at battery posts is 12.87v
v at alternator post is 12.87v

Car turned on:

v at battery posts is 14.7
v at alternator post is 15.1

Soooo is my battery bad perhaps? This is a new battery tender so I can't imagine that it's faulty...

 

Best way to know if the battery is okay is to let it sit 24 hours after a charge. It should sit disconnected from the car. The Batter Tender will float charge the battery at 13.2vdc

 

I think your battery and alt are okay. The cold cranking amps rating should be 590 for the battery with a 110 minute reserve...
What was the original problem one more time????

 

original problem = drove car around for errands on saturday, got home and parked it for a couple of hours, went to move it and it wouldnt start…needed a jump start…once i got it back in the garage, sat it there from saturday night until monday night, and it started right up with no issues…

i am now in the testing phase to try and determine if it was a one time thing or if something is failing/draining my battery...