BIG GUN

Hello everyone,
I'm looking for some ideas to diagnose a charging issue with my 2007 C6 (not looking to bring it to the dealer until I can replicate / diagnose the problem).
The issue has only happened twice so I can't isolate "when" it occurs but I'd like to determine "how" it might be caused.

Conditions:
- Both times were during a long drive / cruising
- Engine temps normal / nothing out of ordinary
- Light throttle

Results:
- Voltage goes from normal ~14v to 16.5-17.5v
- "Service charging system" appears
- I remember some message about "voltage too high"
- Radio & A/C control unit go blank/dead (temporarily)
- Crazy messages appear on DIC: "ice possible", "ABS", etc. etc.
- Blipping the thottle seems to correct it temporarily
- Event usually lasts maybe 30 seconds?

I understand that the alternator has a "requested" voltage from the ECM and an actual output voltage.
I've tried to log these with HPTuners (F and L terminal), but since the condition is difficult to replicate I've never had any results and I doubt the dealer could do any better.

So I'm planning on checking the ground wires. The alternator output wire is moved away from #1 plug wire. The battery is new and starts strong.

Anyone had any experience with the alternating charging at a voltage too HIGH? If so, anywhere I might look to find the cause?
Thanks in advance,
Scott

dembiggins

Sounds like you have a bad voltage regulator or bad alternator

carlrx7

battery

BIG GUN

I'm guessing the voltage regulator is located inside the alternator? I'm up for pulling the alternator out and having it tested but since the issue seems to occur randomly and infrequently, I'm worried it would test fine and the problem will remain.

I'd be less worried if the car didn't flip out when the voltage went crazy. I'd like to have confidence to take the car on long cruises and with all the electronics in the C6, I consider most electrical issues to be somewhat serious.

Thanks for your input.

MARSC6

Sounds like a bad voltage regulator in the alternator. High or low voltage can damage electrical devices. If it is higher voltage get it repaired ASAP.

It could also be a bad ground causing bad readings and everything else to go crazy.

cantrelmitl

I pulled this out of the ASE prepTest: The voltage regulator senses battery voltage, a defective battery such as a dead cell, would lower system voltage and confuse the regulator into thinking the charging system is low and increase alternator output. If the output is high, the battery could be the problem. None the less, take it down to your local Advance Auto and they can isolate a problem like this pretty quick and for free. Hope this helps.
Mike C sends

BIG GUN

Thanks for the input. I'm going to pull the alternator and battery and head down to the parts store for some tests. I'm hoping to receive some results that might give me a direction. It seems strange that with the exception of the 2 instances of overcharging and flipping out the cars electronics (these were months apart), the alternator and battery have performed perfectly with 13-14volts and strong starts. I'll report back with any findings.

cantrelmitl

One last thing, always check your grounds . . . Bill Curlee has an outstanding article on this. I had some wild things going on with my C5 (AC working/not working, radio amp on and off, weird DIC codes) about 4 years ago and thought I was doomed with some harness problem. After reading the article and cleaning all my grounds, all the gremlins are gone. AC works great all the time and no weird DIC codes . . . haven't had a problem since. I also had the infamous battery leak on one cell. It caused my charging to go up but it was there on crank up and went away after running down the road. Thank goodness I got to this before the acid leaked down onto my ECM harness. Anyway, I have used Advanced Auto religiously on battery and alternator tests . . . it's free and our local shop can do a field test on your alternator and a load/charge test on your battery. For the weird problems with no reason or rhyme, I would check your grounds just for good measure. Good luck, I know those type problems are PIA and you definitely don't want whatever it is to go bad in one of those off the road places.
Mike C sends

cranky

clean grounds, load test battery, check and clean the positive cable and alternator wire on the STARTER !!!! you would not believe how many are loose or dirty, causing a multitude of charging problems..............

cantrelmitl

Will definitely add unwanted resistance into your charging system. If you've ever had a slight hesitation on cranking/turnover that is also a symptom of a loose starter bolt.
Mike C sends

carlrx7

steal a batter out of another car

BIG GUN

Well, I don't really trust the guys at the auto parts store to maintain and/or operate their equipment so I pulled the alternator and battery and went to 4 different local stores.

NAPA
Battery = GOOD / Alternator = GOOD (simple old style handheld battery tester / they took the alt in the back)

Pep Boys
Battery = BAD / Alternator = cannot test (guy couldn't determine + from -)

Kragen #1
Battery = GOOD / Alternator = cannot test

Kragen #2
Battery = GOOD / Alternator = BAD (11.4v)!?

So that was incredibly inconclusive! This exercise reminds me why I buy my own tools for automotive diagnosis!

Anyway, I'm planning to reinstall and look into a new alternator. Will check grounds and watch for problem to reoccur...
Hopefully I'll get lucky and be datalogging when it happens to see if I can correlate to something?

LSCHLEM

All that has been said here is good. What I would do is CLEAN the Battery
Terminals. Clean the Hot LEAD at the FUSEBOX. This one can cause problems by loosing contact intermittently. When you remove the terminal see if you can twist it and observe the wire moving inside the Terminal.
Pull the plug off the Alternator and clean the Male pins. Be careful you dont bend them. If all is ok or you found a loose terminal and corrected it,
then start the engine up and put a DVM on the large alternator terminal.
It should be about 14.5 VDC and drop to 13.8 where it normally stays while running accessories . I dont know if you have knowledge about
electronics but if you or someone can get a oscilloscope and test the alternator terminal for noise. That is electrical noise that can drive the ECM nuts with false commands.

Too many times was a Alternator replaced along with the Battery only
to have the condition return. 17 Volts is out of the operating spectrum
of a normal alternator. You have a point about a spark plug or wire that
can generate noise but you need a Scope to see it. Good luck Leon

PowerLabs

Bad voltage regulator on the alternator, for sure. If your battery was bad it would be dragging the voltage DOWN, not up.
You can buy a Bosch remanufactured alternator at NAPA for $277, I suggest you try that...

cantrelmitl

Dang Big Gun,
Sorry to hear about your ordeal. Our Advance Auto down the street does a thorough load/charge/discharge test on the battery . . . dang good test for picking up a dead cell or cell going bad. They also do a field test on the alternator which can isolate the problem between the voltage regulator and alternator. I thought sure one of the folks you named would have had the same type equipment. LSCHEM has a good point if you have any ET type buddies. A Oscope or handheld LCD analyzer could show you the output and whether or not it has noise or is sawtooth. Also as LSCHEM stated, you should check all your contacts, grounds, starter bolt (PIA to get at w/o a lift). Use some NoOx or ground lube equivalent after you wire brush your connections and retighten. Vettes are tough with electrical issues, the least bit of corrosion or looseness can really make for a bad day and problems can be totally random. Not sure I would go the alternators route till you checked those items out, they are pricey. Also, when my alternator went bad I could hear the voltage regulator going bad when I got real close to it, it was a very high pitch whine. Lastly, if you do detect a bad alternator, see if you have a vette club around that can assist with a discount at the local Chevrolet place . . . it will help defray the costs. Last ditch effort, If you have limited mechanics around, I would find a reputable Chevrolet dealer and just take it in, be sure they have some techs that are well spoken about and specialize in vettes. Sorry for your hassle and good luck.
Mike C sends

BIG GUN

Thanks again for the replies..

I'm not stressed about the issue.. I've been through ordeals working on cars before and this is just a little bump in the road. The C6 has a lot of electronics and I don't mind a few gremlins... as long as I can get them fixed!

Regarding the testing, I too was surprised that none of the local shops seemed to have the equipment or ability to really test the alternator and battery... But they all wanted to sell me something! haha

Since the problem is intermittent (2 days in 3-4 months), I'll reinstall, check grounds/connections, and monitor to see if the problem comes back. I also have an extended warranty so I'll plan to pick up a new alternator if the issue persists.

I was hoping to make a concrete diagnosis before moving forward but I think I'm out of options for the time being.
Regards,
Scott

LSCHLEM

In troubleshooting electronic problems. Techs & engineers sometimes
have to develop test devices to get in between the actual component
and the ECM. After about a week of trouble shooting for MAF. MAP for
conditions that turned out to be a Leak. I just completed this little handy device to connect between any sensor, altenator or any component that
is suspected as being the problem and will work in a live situation access
ing dynamic conditions in conjunction with Hp TUNERS. You do need other equipment such as O scope, DVM , Signal generator and other types of equipment that your average garage probably doesn't have. I wish your car with the ALT charging system were here so I could try it. Here is a pic.
It's just a simple connector access.

LSCHLEM

Here it is.

0Chuck CoW

It's very safe to say.....that your alternator is no good.


07 Corvettes have a tendency to have alternator problems.

If you have ever made WOT accelerations to redline with aggressive shifts
then you have the potential to kill an 07 Corvette alternator.

I have at least 4 or 5 alternators FROM 07 CORVETTES ONLY that failed immediately after WOT shifts.

The centrifugal forces inside the alternator (keep in mind that the cooling fan of the alternator is INSIDE the unit and not outside) cause the cooling fan to "GROW" with high rpm and cause the fan to short against the field windings causing the regulator to fail, the diode to fail, or the field to become directly shorted.

Sometimes they will smoke, smell like burnt plastic, or just not charge.

I have seen on occasion that they set a "service charge system" message and code and after clearing the code they drive fine for years....

Trust me.... 07's don't last.

Chuck CoW

LSCHLEM

These are the things that experienced people like CHUCK COW have seen. Perhaps I should consider getting my alternator PORTED.
LOL