antitheft stays on drains battery

Greetings, It is highly unlikely that the antitheft LED is causing the parasitic drain on your main battery as Most modern cars with a factory-installed theft deterrent system use a low power LED that draws between 5 and 10 mAmps. That is a pretty insignificant amount for a good 12volt 600+ cranking amp battery.

I would start with testing the battery, then testing the alternator then working my way through the fuses to start tracing what might be causing the drain. I would start with anything that was not installed at the factory.

Items high on that list would be

1. Aftermarket Installed Radio / Stereo
2. add on lights.
3. add on trailer harness.
4. any additional wires attached to the battery or fuse box that don't look factory.

That is the big 4 in my experience.

I would start with this procedure.

1. Check to make sure you have a solid 12 volts at the battery. If Yes move on. Use a standard meter. You can buy one cheap just about any hardware. Set it for voltage 20
2. Make sure that everything in the car is turned off there is no key in the ignition and all accessories are removed. Phone chargers etc.
3. I would leave the voltmeter on the battery and gauge what kind of draw we are talking about. i.e. how fast is the voltage going down. Is it draining at a very fast rate? couple volts an hour?
4. If I didn't see a measurable change in voltage and it holds 12 volts. I would immediately test the alternator output.
5. If the alternator is failing it could be only putting out a small amount of voltage that would not be enough to run the car and additionally charge the battery. This happens often in the 90's models fords. I had a bronco II from 94 and it wouldn't show a battery on the dash for a charging system failure but it had a charging system failure.

It is free usually to go to any parts store and have them test your battery to see if it has a dead cell or needs to be replaced. Its also usually free to have them test the alternator as well on the test machine. Its more likely that one of these two components is failing or both and that you need to replace them then the antitheft draining your battery.

If you do find a measurable change while the car is sitting cold. I would begin removing fuses until i found the circuit that was shorted and causing the drain on the battery. I have seen a fuel gauge on a vehicle with a dead short that would drain a brand new battery in about 12-14 hours. So anything is possible.

Good Luck and good hunting.

If I can be of any further help just post up a response.

Monte