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My trucks battery slowly drains so in about a week it’s dead. I rewired the truck with a Painless universal kit and it’s got a new Optima battery. With the burglar alarm and radio slowly draining power it still should go a month to 6 weeks without draining the battery dead. How would you go about trouble shooting this to find the location of the problem?
In general, I would disconnect the constant power to the alarm and radio, then put a voltmeter on the battery and pull fuses one at a time until you see the voltmeter increase. That way you can at least isolate which circuit has the drain. If you can't find the drain, hook the alarm and radio back up one at a time and see how much power each of those eat.
Here's the easist way to do it. Use a testlight like the picture shows, and pull the fuses. Be careful about the domelight, since it will cause a false drain if it's on during the test. If none of the fuses make the light go out, then pull the wires off the alternator and see if the light goes out.