Needed:
Battery tester with 10-amp DC range
Step1
Charge your battery if necessary. Dead batteries (and even weak ones) don’t give accurate results on a draw test. The dome light is a good indicator of battery strength. If the light is weak, pulsating or refuses to turn on, you’ll need to charge the battery.
Step2
Shut off everything in the car. Pull the keys out of the ignition. Ensure all service lights are off, lighted compartments closed and doors shut. Open the hood, and disconnect the trouble light underneath if your vehicle has one. Wait for 30 minutes before moving on to Step 3. (This enables normal drain from interior components to finish cycling.)
Step3
Set your battery tester to 10 amps DC. Disconnect your positive battery connection (red cable) and position it safely away from metal components. Connect the meter’s positive probe to the battery’s positive post while simultaneously holding the negative probe in the air; keep it away from anything metal.
Step4
Place the negative probe on the end of the removed positive cable to complete the circuit. Yes, you’re putting a negative on a positive. Yes, this is ok. If you have a severe drain, you’re likely to pop a fuse or two—identifying your problem.
Step5
Check the meter reading. A normal reading is usually under .035 amps. If you have a minor drain that causes a higher reading, you’ll need to check each component.
Step6Remove the first fuse in the box, and check to see if the load problem is resolved. If not, replace the fuse and check the next one. Repeat the process with all fuses. If the fuses check out fine, you have a wiring problem.
Step7
Remove the tester and reconnect the battery. Follow the hot wire to the next connection. Remove the positive cable and connect the positive probe of the tester in its place. Connect the negative probe to a metal object. Check the meter. If the drain isn’t resolved, reconnect as normal and follow the hot wire to the next connection. Repeat this step at each connection point until you narrow down the problem.
http://www.ehow.com/how_2249402_find-parasitic-battery-drain.html
