Hello everyone,

I own a 2006 C6, which has been having some battery 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
- 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.
- replaced the battery terminals for the car, as mine were getting kind of, old.
- 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 have used the trick where I hold the Accessory button down for 10 seconds, and checked the voltage level there, it was at 11.5 and only dropped down maybe .1v-.2v when turning on headlights.

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 has been internals, minus the exhaust. A friend suggested I add an additional grounding cable off of the battery to see if that helps. If anyone has any ideas as to what could be causing this issue, please let me know, thank you!

 

What starting issues? Has the car left you stranded, wouldn't start due to a dead battery? And are you using the DIC to measure voltage? The DIC is notoriously inaccurate, there's about 5 grounds that can influence what voltage the DIC displays. I was obsessing over the DIC readings until my mechanic asked me these questions. I remember a thread in this forum that said if all the grounds are not clean and tight the DIC will show as much as 2 volts less then the alternator is producing. Do a search, there's a couple of GREAT threads on the charging systems of our car...good luck!

 

Check and make sure the ground wire is not corroded and making good contact with clean metal. If not take off and clean throughly, re- attach and coat connection with dielectric grease, to keep corrosion from forming. Next, I suspect your battery is not holding a charge, possibly because of too many drain and charge cycles. Replace batter and keep a maintainer on when not driving. Good luck

 

Given the list of items replaced and there's still a draw?
Have OnStar?
Even if not an OS subscriber its been reported [here] several times a defective OnStar module resulted in damned thing staying 'on', causing dead battery.

Pull OnStar fuse, you'll see if OS module's the culprit right away.

 

Keep it on a battery tender when not being driven.

 

:Battery cables. Have the replaced the ends lately? What is the voltage drop from the post to the cable? Cables are sold as a set.

 

Mine is an 2005 and it needed the BCM replace as well