Optical TDI

There is a faint noise coming from near the drivers side windshield wiper under the hood. In my quiet garage, if I put my ear up to the driver's side windshield wiper, I can hear a faint buzzing sound as if something is running/operating while the car is off.

This is continuous even after the car sits for over a day. The key is not in the ignition and the car is not locked.

I believe this noise is causing my battery drain. It's a 4 month old battery, but after 2-4 days of sitting in my cold garage the battery doesn't turn the motor over nearly as fast, plus the voltage has decreased to just below 12v.

I don't think it's a faulty battery due to the buzzing sound - what is this sound?

ivangene

doesnt sound right...

you have CPO - take it in, get it fixed

Barn996

I thought a locked porsche had less drain on a battery than an unlocked one.

Optical TDI

Good advice. I just put in a service request.

TomF

These cars draw a lot of power. It doesn't take much to tip the balance and drain the battery. My car is supposedly the biggest power pig of them all: C4 cab, tip, nav, litronics, heated seats, etc... Even with a new battery and alternator, I watch my power consumption. My nav never really shuts off unless I lock the car. I am going to upsize to the biggest battery (CCAs) that I can fit in there when this one dies.

With everything on at once, my voltmeter hovers just above 12.1 volts... not much margin for error. The biggest draws are the heated seats, no surprise there, rear defogger on the hardtop and the litronics. With the engine running and warmed up, I am at 14V.

I have also heard that the 996 is infamous for not going to sleep after you shut off the engine. Many systems stay active until you activate the alarm and lock the doors...I would definitely lock the car even in your garage. Don't forget to leave a window open in case the battery fails! LOL

wwest

Litronics only draw 35W/side whereas halogen 55W/Side.

TomF

I had forgotten that the litronics are so low. I regularly use my fogs at the same time, and I think that they are aftermarket bulbs- they seem much brighter than 55 watts.

Optical TDI

Problem solved: it was the alarm horn making a faint, but continuous noise. Not sure if that is the actual cause of the battery drain...time will tell.

Ahsai

James, my car has the exact same noise but it goes away in a few hrs after the car is stopped and left unlocked.

I used this clamp meter on the battery cable to test current draw http://www.thetoolwarehouse.net/p-11...lties-685.aspx

With the car parked, not locked, all doors closed, front trunk light removed but with the lid open, there is ~5A draw for a few minutes, then it stays at ~300mA for the next 3 hrs and then it goes to ~0.

Optical TDI

Gotcha. It seems that mine probably never went to a near 0 draw.

TomF

Glad to hear that you got it sorted out. I noticed today that power indicators on the computer of my nav system stay illuminated until I activate the alarm. I have the PCM1 and I am wondering how much it draws if I don't start the alarm. Time to grab a meter and check.

kristyhana

I was told by my mechanic to always lock and arm the car because otherwise it will drain the battery because it is still on like standby mode until locked/armed.

StephenB

+1 A clamp meter is an excellent tool for finding the unwanted draw. I like the Extech that has 1mA resolution. FYI 300mA seems high...my car is around 40mA after 15-20 minutes

http://www.sears.com/shc/s/p_10153_1...u=03499977000P

Ahsai

That's good to know. I always thought my 300mA is on the high side too for 3hrs. So your car goes to 40mA after 15-20 minutes with the doors locked or not locked?

StephenB

I verified for someone on the GT3 forum. Take a look over there. I tested both locked and unlocked.

https://rennlist.com/forums/996-gt2-...n-2004gt3.html