Abnormal Parasitic Battery Draw

[gmarcucio]

2008 Corvette Vert with 20,000 miles and I have a abnormal parasitic battery draw that kills the battery about every 1 1/2 to 2 days. I am a high school auto technology teacher and can certainly perform a starting/charging system and parasitic draw test but obviously I know I have a draw with a dead battery every 2 days. Sometimes finding the draw can be a pain too. My 3 year/36,000 mile warranty runs out the 24th of this month. What should I do? Check it out first myself or just bring it to the dealership. I hate having someone else work on the car but I would also hate to pay for a PCM or expensive part. Or... have them say that I messed something up. I did the obvious checks like one TSB said to do. Charge battery, get in vehicle. Don't start it. Check to see after 90 seconds if everything goes off (including the Nav) and it does. Can anyone else that had this problem tell me what the cause of their draw was?

[Kuelblaz]

Originally Posted by gmarcucio

2008 Corvette Vert with 20,000 miles and I have a abnormal parasitic battery draw that kills the battery about every 1 1/2 to 2 days. I am a high school auto technology teacher and can certainly perform a starting/charging system and parasitic draw test but obviously I know I have a draw with a dead battery every 2 days. Sometimes finding the draw can be a pain too. My 3 year/36,000 mile warranty runs out the 24th of this month. What should I do? Check it out first myself or just bring it to the dealership. I hate having someone else work on the car but I would also hate to pay for a PCM or expensive part. Or... have them say that I messed something up. I did the obvious checks like one TSB said to do. Charge battery, get in vehicle. Don't start it. Check to see after 90 seconds if everything goes off (including the Nav) and it does. Can anyone else that had this problem tell me what the cause of their draw was?

I know this is gonna sound obvious, but have you checked the Battery for a short? I recently spent a whole day trying to figure out a similiar problem ... it was the Battery, duh! Sometimes I get wrapped around the wheel with 'diagnosing' the problem and it turns out to be something obvious that I skipped ... and like you, I am a mechanic by trade!

More than that and I'd take it to the dealer, especially since its under warranty. Need to get that kind stuff documented against the VIN. Could be something really simple, but you paid for the warranty, make them figure it out.

Good Luck!!

[Y2Kvert4me]

If you've been letting the battery "die" to the point it won't start the car, it's likely junk even in the event it's not the root cause. (though it usually is).
Unlike a deep cycle, starting batteries are not tolerant to being that deeply discharged. Each time it happens, the battery loses capacity, and it loses what charge it does have much quicker, even without an abnormal parasitic current draw. (which should be no more than 20mA or so when the car is in "sleep mode").

Letting it go dead once or twice you'll probably get by with and successfully recharge it to maybe 80% capacity, and on a daily driven car, it may seem fine and last a while like that, but realize the damage is already done and that battery is never fully recharging, and never will again.
If the battery has gone dead more times than that in it's lifetime, the battery is junk, period.

Drop a new battery in it, and I'll bet you can let the car sit for the next month and it'll start up just fine.

[gmarcucio]

I'm going to put the Snap On MicroVAT on it today and check the battery and charging system. The MicroVAT applies a load electronically rather than using a carbon pile which is recommended for newer vehicles. I already have an appointment at the dealer for Thursday.

[gmarcucio]

I connected the Snap On MicroVAT and selected the Battery test option. The message I received was " vehicle interference, turn off all accessories."
I'm thinking the tester can see the draw on the battery and does not allow me to do the test with the draw.

[Y2Kvert4me]

I would isolate the battery to test it.

But if you're convinced there is a draw, what current readings are you seeing when the car is in sleep mode?

[gmarcucio]

I didn't want to disconnect the battery (even with a battery power saver plugged into OBD II connector) because I don't want to give the dealer any reason to point the finger at me and say I was the cause of any electrical component failures from spikes or whatever. The battery has never been disconnected in this car. I just thought I would check the battery with the MicroVat myself before I brought it to the dealer this Thursday. I didn't realize the MicroVAT would give me that message. If I was able to get a battery test and the results were bad battery I was going to call dealer and ask them if they wanted me to replace battery prior to my appointment. Of course if I was going to replace battery at that point I would check and see if draw was still present. I let the car sit overnight and put the MicroVAT back on this morning. I didn't get that message anymore and the battery and alternator both tested good. Now I guess I'll just wait it out and bring to the dealer on Thursday and let them search for the draw.

[pappytinker]

Have you checked to make sure that you have not inadvertently turned on the map lights on the mirror (knee might have hit the button to the left of the steering column)?

[WarDriver]