Battery Draining fast

[SkullZ]

Sorry if this has been asked, I am new here.  I have a '78 C-10 Scottsdale with a 350 that I just got less than 2 weeks ago.  As soon as I got it in the garage turned the engine off it would not crank over.  I assumed dead battery being that it was setting for a while.  Put a new battery in this past Saturday and drove around for a while, the battery gauge showed over 13V the whole time I was driving, did not see what it was reading while starting tho.  Monday went out to start it and...nothing.  Check battery and it had 0V already.  My first start will be with the stereo system as it looks like it was just slapped in by the previous owner.   Any suggestions would be appreciated.

[Shifty]

See if it's obvious first.

Then the easiest thing is the negative cable and test light trick.  Pop the negative cable off, and run a test light to it to see if it's still got power.  If it does, something is still drawing voltage, so start pulling fuses one at a time until your test light goes out. 

[SkullZ]

Put the test light in series with the Negative post and cable?

[Shifty]

Correct, clamp on the cable terminal and the needle on the battery post/anode.  If all is well, there will be no light. 

[bd]

Application Notes:  Make sure you use an incandescent test light, not LED.  Make sure the ignition is switched off, the cabin doors are closed, and the headlamp switch knob is rotated fully CW ensuring that the dome/courtesy lamps are switched off.  Any significant battery draw will illuminate the test light at normal full brightness; less than normal full brightness indicates an insignificant draw; not illuminated indicates zero draw.

Is there a factory GM clock in the instrument cluster?

[Shifty]

Thanks BD, I had forgot about the LED thing...

[SkullZ]

Application Notes:  Make sure you use an incandescent test light, not LED.  Make sure the ignition is switched off, the cabin doors are closed, and the headlamp switch knob is rotated fully CW ensuring that the dome/courtesy lamps are switched off.  Any significant battery draw will illuminate the test light at normal full brightness; less than normal full brightness indicates an insignificant draw; not illuminated indicates zero draw.

Is there a factory GM clock in the instrument cluster?

No these is no factory clock.  I'll have to check my light too, can't remember if it is LED or not.  Thanks for the heads up on that.

[SkullZ]

Correct, clamp on the cable terminal and the needle on the battery post/anode.  If all is well, there will be no light.

Thanks for the help

[Shifty]

Also....if you do find which circuit is drawing the voltage, it only gives you a starting point to find the issue....it may be something like a bare wire, burned wire or shorting-out accessory. 

Don't trust factory gauges, BTW, they aren't always accurate.  To get to 0 volts in that short of period usually means it's something pretty heavy.  Check all of your grounds and cables as well, making sure that the cables are flexible without a "crunchy" feel, and no white corrosion powder. 

[bd]

Visually inspect the full length of the B+ cable between the battery and starter, checking carefully for cuts, abrasions and melting, especially where the cable runs near the frame rail, through retaining clamps, and in proximity to the exhaust manifold.  Check the cable connection to the starter solenoid to make sure it is tight and not shorting against adjacent starter wires.