Hello all.

This is my first post in the C6 Tech section, I was previously a long time C5 owner.... I purchased a 2012 A6 Grand Sport Coupe a couple of months ago. The previous owner had installed a few modifications to the car. (Morimoto Headlights, Kenwood touchscreen radio headunit & backup camera).

I have driven the car maybe around 15-20 times with no issues. I have started the engine up probably at least 30 times before the incident. The battery installed in the car is dated January 2022.

Now to get to what happened.... I drove the car maybe 10 miles, got out, parked for maybe 2 minutes before I walked back realizing I needed to drive a few more blocks to reach my intended destination. I opened the electronic door handle, got in & closed the door and immediately pressed and held the push to start ignition button. The entire car immediately went dead/silent. There was absolutely no power at that point...couldn't even get the driver's door open without using the emergency release.

I waited a few hours for my son's little league game to get over, tried going back to the car to see if it would "wake up", but never did. Even the tiny little red lights for the door handle indicator wouldn't light up. I ended up bringing my pickup back, with the intention of jump starting the 'vette.

Before jump starting, I took a voltage measurement, and I had 12.55 volts on the battery. I didn't expect to see those numbers, so I took a wrench and disconnected/reconnected the positive battery cable....and the corvette suddenly came back to life. I jumped inside and the engine fired up immediately, and I drove it home.

I did notice that the instrument cluster had reverted back to the previous owner's name & settings on the display. Also the radio headunit was prompting the initial install configuration menu, like it was brand new again.

The car seems to be fine now, but I have never seen this type of behavior in any vehicle I've ever owned. The battery had good voltage, but wouldn't pass power to any device inside of the car. Does anyone have any thoughts or ideas?

 

Clean ur connection. these cars are notorious for this problem

 

Poor connection somewhere. Could have been the positive terminal you put the wrench on, corroded cable, or elsewhere in the electrical system.
Odds are high it was the battery terminal since you resolved the problem when you put a wrench on it.

 

A loose ground on the battery will kill everything. Don't ask how I know.

 

A battery terminal cleaning tool like works wonders. It is a must for my toolbox.

 

I ended up buying the battery post cleaning tool, and had the dealership replace the battery cables & clamps, and hoped that my problem wouldn't come back. (My battery posts & clamps visually appear to be flawless)


I experienced this malfunction again this afternoon. (This is the 4th time in just over 1 year of ownership). It always happens, as soon as I press the ignition button after entering the vehicle. (The car had lights & power up until I pressed the push-to-start button).

I was thoroughly prepared for it this time, I had a socket wrench in my hand, pulling off the battery terminals within 60 seconds of the malfunction. Here's where it gets very weird...

I pulled both battery terminals completely OFF, and let the car sit like that for about 15 seconds. I then put both terminals back on, and tightened them on very tight. The car is still completely stone dead, and didn't even get a hint of a spark out of the battery post making contact with the clamp. I repeated this process about 5 times. I finally threw in the towel & called my wife to come pick up my son & I, leaving the battery disconnected.

After what I estimate to be around 10 minutes following the malfunction, I gently placed the clamps back on the battery terminals, and saw small "sparks of life" that you would expect to see when connecting the positive terminal. My son confirmed that the car had interior lights once again. (this is without even tightening down the clamps). Car started without even a slight hiccup, and drove back home without issue. I can't help but notice that this behavior is striking me as oddly similar to any generic electrical device that is equipped with an auto-resetting current overload.

Wish I even knew what direction to look.

 

i bet if you just touch or wiggle the positive cable terminal the power will come back on try it next time

 

If the B+ post on the under hood fuse box is loose (pictured below) or you may have a bad fusebox the under hood and IP fuse boxes will be dead as a door nail….if you have a 12 volt test light when you have no power just start checking fuses with the test light under hood and in the IP Fusebox…a lot of fuses have battery power with the car off…just a guess…I see you had both battery cables replaced…you’ll have to unfortunately get underneath the car to check their work and make sure the both connections are tight…the engine block ground may be loose…to check that connect your test light to ground and have someone try to start the car…if the test light illuminates NO GOOD…you may wonder why the test light will illuminate ??....think that the test light is another "bridge" back to battery negative...with a bad block ground there will be a lot of electrons trying to make it back to the battery...the test light is another bridge so electrons will go through the test light instead of the battery cable so the test light illuminates...if you have the OE battery terminals change them…they’re junk !!…also you ALWAYS disconnect battery negative first and reconnect it LAST...also HIGHLY doubtful the cables were bad...the dealership could have easily performed a voltage drop check on them to verify...you could have saved a lot of money there.