M20J Corvette

The car is a 2007 Base 6 speed convertible with 30,000 miles.

The car was parked in my garage for about two weeks while I was away. I tried to start and it acted like a dead battery – starter relay clicking and lights dimmed when trying to crank. Dash voltage showed 8.6 volts.

I put the battery on a charger overnight. Car started right up and ran fine. First thing I noticed was that the voltage on the dash display was fluctuating between 13.6 and 14.2 volts with the engine running and a moderate electrical load – A/C and headlights on. Previously it was always rock solid at 14.2 volts.

I verified the dash voltages with a multimeter on the battery. Readings were within 0.1volt

Shut the engine off and voltmeter across battery terminals read 11.3 volts. I charged the battery again – reads 12.7 volts, reconnected and voltage dropped to 12.3 volts and kept dropping.

Since the battery age was unknown, replaced battery with a new Autozone Gold 660CCA battery.

Started fine and drove the car. Same voltage fluctuations under load. Let it sit overnight and next morning same thing. New battery showing 8.6 volts, had to charge the battery to crank the engine.

Obviously something draining the battery, checked all the lights, switches, everything is off. I’m puzzled as to why, suddenly, something failed that would cause the battery to drain.

RicK T

Yup, you or someone will need to do a battery draw test after shutting off the car.

This is a long discussion with good info but if you look at post 77 and beyond you will see examples of what your draw test should look like:

https://www.corvetteforum.com/forums...yndrome-4.html

Then if you confirm excessive current draw you have to start unplugging fuses or modules until you ID the culprit. Good luck.

extrapilot

Silly question but do you have anything plugged into the acc. sockets at the ash tray or center console?

M20J Corvette

Ran the draw test Rick suggested. I was seeing high draws on the order of 3 to 5 amps.

I brought the car to a local independent Corvette shop. Even after driving 40 miles, when I shut it off in their lot it wouldn't start 30 minutes later.

First thing they did was run a diagnostic. The tech found 81 codes in the computer, including "No communication with BCM, PCM and ECM". He said he's never seen that many codes stored.

His theory is that from trying to crank with only 8 volts in the battery it caused a voltage spike and set the codes. Then, because the various modules were stuck in an endless shutdown/initialization loop they caused a high draw and killed the battery after I charged it.

Anyway, it sat for two days in the shop. and started fine each morning. Its home now. I'll let you know in the morning.

Thanks to all who replied.

RicK T

Hope it's fixed.

Cziffra

I have an issue that I hope someone can help me with. Due to getting a hip resurfacing I was unable to drive my 2010 Callaway SC 606 Grand Sport auto-trans from Aug 8th until Sep 13th. Someone started it once a week and let it run for 20 minutes. On the Wednesday took a drive first time in 5 weeks, no problems at all, went to take a drive today, Saturday the battery was dead , had it jumped,according to the manual, started right up. Was going to buy a new battery and when I shifted from Park to Reverse the tranny banged and the car wanted to jump, same with Drive to Reverse. The check Engine light is on and the windows would not index. Only drove a few blocks and put it back in the garage. Of course I'm certain I'll need a new tranny, but perhaps some of your folks could give me some advice or info. Much appreciated.
Best Frank

Cziffra

Sorry If I put this up in the wrong thread, just learning how to use the forum.
Frank

extrapilot

These kind of issues can usually be contributed to a bad battery, as the voltage is not strong enough to operate the trans module correctly.
I would go ahead and get the new battery, re-index the windows and see how it drives afterwards.

M20J Corvette

Follow up on my post of 9/14. This gets stranger and stranger.

Two days later, it was dead again - down to 8 volts and would't crank.

This time I brought it to a large Chevy dealer who sells lots of Corvettes and came highly recommended.

They said the Autozone battery I installed, had a dead cell and failed a load test. They replaced it with an AC Delco battery. Let it sit over the weekend, started fine on Monday. I drove it home and it's been fine ever since.

I was able to return the battery to Autozone and to my surprise, got a full refund no questions asked.

For the next two weeks drove around with the original AC Delco battery and jumper cables in the trunk, just to be safe. Interestingly enough, the original AC Delco is still holding a charge.

I'm still not convinced the problem is solved but at this point there is not much else to do.