Cadillac Repair: alternator, ampmeter, minuits

Question
hello

 id like to know how I can tell whats causing my battery to drain, I have a caddy 1987 coupe de vill 8 cylinder, can it be the voltage regular ? where is it located ?

Answer
Hi David, Sometimes this can be a search and destroy mission. If the drain isn't happening all the time it will take some good investigating to find the drain. It could be as simple as looking in the car, under the hood, inside the trunk and under the dash by the glovebox at night to see if a light stays on when it shouldn't. The voltage regulator is inside the alternator and unplugging the plastic wire connector is the test for that. If the draw goes away then the regulator has shorted internally and will need to be replaced or the alt. will have to be replaced. There are 2 ways to check for draw. 1 is with a 12 volt test light hooked up between the neg battery cable and the battery negative terminal and after 20 minuits with the key out of the ignition you still get a half bright or bright light then fuses will need to be removed and replaced one at a time until the light dims. Then you need to unplug things on that circuit until the light again dims. Then replace that part and your draw might be gone. The second way is to substitute an ampmeter for the testlight and when the draw is less than 20 milliamps then the draw is gone. Make sure you use a clamp style meter capable of reading milliamps or a meter that is protected to 20 amps. Hope that helps. Bill