Disconnect your Negative Battery Cable.
No KEY in the ignition switch.
Connect your DVOM (Digital Volt Ohm Meter) as follows.
DVOM in the "off" position
Connect the Positive lead to the 10Amp Socket (usually a separate one)
My meter has the Square lead in to the 10Amp socket, my other leads are soldered into the meter.
Move the meter dial to the 10A section.
Connect the Negative lead to your disconnected Negative battery cable.
No Key in the ignition.
Turn your meter on.
Do you have 0Amps or .050Amps That is a good sign.
If you have anything else, go in to the Fuse Panel and Remove one fuse,
then check to see if you have less on the meter Yes/No.
Yes, you are finished. Now you have to narrow down what is on that Circuit that may be causing the drain. Usually after market installed radio's /subs
No, replace that fuse and pull the next one, until you have the best reading that you can see on the Meter.
If you have removed all the fuses and there is no change, then remove the additional
wires that are attached to the "positive" battery cable. If you have removed all your
additional wires, then remove the "positive Cable to the main battery positive post.
You should be at 0 now.
If not, then depending on your cables you are looking at a bad starter/alternator.
Your Alternator should be an additional large wire connection on the Battery. You will need to reattach it to the Positive Cable.
Remove the Positive cable from the battery (you need it disconnected for a bit).
Remove the 2 Phillips screws that hold the Voltage Regulator in the alternator and remove it.
Reattach the "Positive Cable" to the Battery does it go to 0? Yes bad voltage regulator. No Bad Starter Usually.
When Finished
Turn Your Meter OFF (Do not Change the Dial).
Disconnect the Meter.
Remove the probe from the 10A socket and replace it in the other.
FAILURE to do these last three steps will result in a "FRIED" meter
