Brand new battery and won't start
 

2008 Porsche 911 Carrera ,manual 6 speed:
I have a new battery in. Mind you I have gone through 2 other batteries because if I don't use it after 3 days it dies.I checked every fuse and couldn't find a current draw. I gave up last year out of frustration . Now that spring is almost here I started on the project again. It says depress clutch.
I have bypassed the clutch starter switch(white) and also red one . Just to to see if they were the problem. My fans turn on almost immediately when I try to start it. It does not even crank.
Any ideas? Also what kind of reasonably priced Porsche obd2 code reader would you recommend?

Lisa and Chris: This forum is for the most part about air cooled models. You may have better luck in the water cooled side of the page.

Clean all grounds!

Sorry about this, your car has a serious current drain somewhere. Have you pulled every fuse one at a time to see if that would identify the bad circuit. These cars should easily go three weeks without killing the battery.

Basics first.
Battery cables could be loose/oxidized, clean and reattach tight. Check voltage see how dead it is, you’re probably at 12.4v if fans are turning. You’re not completely dead or drained so do a proper charge with battery disconnected (not a battery tender overnight) but a dedicated battery charger. Recheck with multimeter for 13v or more. Get it started and get a load test see if the alternator is putting out at least 13.5v.
Wouldn’t be the first time a new battery fails off the shelf.
So many modern possibilities, nasty culprit is a faulty stuck relay, door locks, windows, sunroof any accessories for that matter. Another gremlin is the electronics are waking the car up too often with close proximity to the key fob. Ugh, remote start too. Any weird alarm issues?

Glad I’m analog - crank windows, lock knobs and no OBD.;)

Use a Multimeter to help find your battery drain with key off
 

Hey, it doesn't matter the year of the car as this will help find a parasitic draw on most any car.

In a nutshell you are going to use a multimeter to show an amp draw by removing a cable off of your battery and attaching one lead from the meter to that cable and the other lead to the battery post that you removed the cable from. Then put the meter in the DC AMP setting and if you see a draw then you have to now find it, which can be a pain!

Basically the meter is now serving as the battery cable, the current from the battery is first going through the meter and then to the car and any amps being drawn will show on the meter.

If you see any amps being drawn with the key removed you will start removing the fuses one at a time to see if the draw goes away.

Start with the most likely culprits by searching for your year make/model with keywords like parasitic amp draw and the like, that way you can start with the most likely fuses and go from there.

It's hard to describe what I am asking you to do but I found this video that may help.

https://www.youtube.com/watch?v=-uW5e-sLK0o

I have actually done all of this. Current state car doesn't even turn over. Put key in and fans start and I get depress clutch pedal. I have bypassed that switch and it still doesn't start. It worked perfect one day and then the next won't. I've looked all wires over all fuses over. Used multimeter

Do you leave you key fob in the car in your garage ? A water cooled owner friend of mine discovered this the hard way. It energizes multiple circuits in the car when within range, and that does relate to a current draw. Sounds silly, but there it is.