Drove my '13 GS to work on Thursday, no problems. Saturday, it would not let me open the door until I hit unlock on the remote, then it would not crank. Just a lot of clicking when I hit the start button. So I connected my super capacitor jump pack, waited about 2 minutes for it to charge up and the green (14V) light to come on steady. Hit the start button and it fired right up. Drove around for about 20 minutes, was seeing about 14.2 V in the DIC. Stopped to buy groceries for about 30 minutes and it would not crank again. Used the jump pack again and drove home. Disconnected the battery, charged it until the charger went into float then removed the charger. Battery voltage only 12.4, not horrible but low. Looked up how old the battery is, 5.7 years. Bought a new battery, checked the voltage, 12.98. Put it in, fired right up. Took it to the coin car wash, washed it down, wiped it off, less than 20 minutes. Would not crank!!! Son of a bitch. Can't be the cables or connections. Do I have a current drain? Already have the dual mode exhaust fuse pulled. Guess I'll pull the OnStar fuse. Don't have an inductive current probe, just a multi meter. Where do I go next?

 

Fully charge the battery and with your DVOM on the AMP scale remove the negative battery cable and put the leads of the DVOM in series between the battery post and battery cable…close all the doors and keep the FOB away from the car and read the amps or milliamps on the DVOM after the modules “go to sleep”…around 15-20 minutes…the max current draw should be no more than the Reserve Capacity of the battery divided by 4….if 100 minute RC max drain should be no more than 25 milliamps…if you do have a drain and the battery keeps discharging the battery service life is GREATLY reduced…my inductive clamp on my scope tends to drift after a while so I use the DVOM.

 

Set your DVOM for DC voltage and hook the red lead up to the positive battery cable connection on the back of the alternator and the black lead to a solid ground. Start the car and you should read about 14+ volts or higher. This will confirm the alternator output is sufficient. While the car is running move the DVOM to the battery; red lead to positive and black to negative or a solid ground. You should read a slight drop by a few tenths from the alternator reading. If you find a larger drop by a couple of volts or more, then suspect the battery/alternator cable connection on the starter solenoid. You would need to secure that connection to read higher voltage on the battery sufficient to keep the battery charged.

Report your findings.

GD

 

The car has been sitting with the battery disconnected for 3 days. Opened the hatch with the key and checked the battery voltage, 12.59 V. My multimeter can only read up to 10 A. Connected the battery through the multimeter, car alarm goes off pulling 13A but it didn't blow the fuse in the meter. Connected the battery directly and turned off the alarm. Hooked the battery up again through the meter and watched the current. It started out around 6 A, gradually came down in a few steps. When the interior lights turned off it was down to about 1.5 A. After a few more minutes it shot up to 5A briefly then dropped to 0.01 A and stayed there until I got tired of bending over the tail. I need to get some alligator leads so I don't have to hold them!

Hooked the battery up directly and started the car. Cranked pretty well. Immediately checked the voltage at the battery terminals, 14.6 V. Checked at the jump terminals under the hood, 14.6 V. Closed the hatch and checked the DIC, 14.4 V (can't get the DIC to show anything with the hatch open). Drove 3 miles to the gas station. 14.3 on the DIC at 1500 - 2000 RPM, 14.1 at idle. Shut it off and checked at the battery, 14.39 V. I'm assuming the car was drawing 5-6 A so probably normal. Filled the tank and drove home. More traffic and hotter engine so voltage slightly lower, 14.1 cruising and as low as 13.7 stopped at a light with AC and engine fan on.

I'm going to drive it to work tomorrow and see what happens.

 

Could not get in this morning, a sure sign of low valtage. I was already late so I just jumped in my truck.

 

Pull the onstar fuse in the passenger footwell. Get a new battery. Add the big 3 wire kit. Cut off the POS battery cable clamps and replace with new ones from autozone.

I can leave my car parked for 3 weeks with no battery tender and fires right up.

 

Already replaced the battery and until last week I could leave it for 3 weeks too. I am going to pull the onstar fuse. Never heard of the "big 3 wire kit", can you do that with the battery in the back?

 

https://www.saccitycorvette.com/C6Big2.html

here you go.

if the battery drains once. I’d replace it again. It’s never the same after

 

Had a similar problem with another car. Negative cable was only holding on by a few strands of wirer. I would also check the positive wire.