I have to put battery on charger just to get it to turn over, after it sits any longer than a day. But if I leave it disconnected, then hook it up it, it spins over nice. I have noticed that when reconnecting the NEG. cable it sparks, so I put a voltmeter in series with the neg cable and post and I'm getting 12.5 VOLTS! I tried pulling all fuses and still same result. Where should I look next?

Other possibilities are the charging system,
To test for the drain, disconnect any clocks and radio with memory, with the car off and everything turned off, (make sure car door is shut to keep dome light off) disconnect a battery cable and connect a test light inline between the cable and the battery, with a drain the light will be lit. You need to make the light go out to find the drain. Disconnect things one at a time till the light goes out. First disconnect the alternator and voltage regulator plug, then fuses at the fuse box.

Voltmeter shows the voltage drop across the cable to battery terminal. Across an open circuit (what you have when the cable is disconnected) the voltmeter will always measure the source(battery) voltage.

What you meant to do was put an AMMETER in series with the cable and battery, and you can measure the current draw through the circuit.

The suggestion of using the test light is a good one, any drain big enough to empty the battery after one day should have enough current to light the light.

Technically speaking you don't have a short, a short would kill things VERY quickly, but you do have a drain of some kind, you need to removed things from the electrical system one at a time to find what it is.

Did you have the door open, when you were checking for a draw? Have seen many mechanics do that. Not sure if you pulled all fuses at once, or one at a time? Unplug alternator, and voltage regulator and see what happens
Good luck

Thanks guys, I'll try all the above and post back.

Voltmeter shows the voltage drop across the cable to battery terminal. Across an open circuit (what you have when the cable is disconnected) the voltmeter will always measure the source(battery) voltage.

What you meant to do was put an AMMETER in series with the cable and battery, and you can measure the current draw through the circuit.

The suggestion of using the test light is a good one, any drain big enough to empty the battery after one day should have enough current to light the light.

Technically speaking you don't have a short, a short would kill things VERY quickly, but you do have a drain of some kind, you need to removed things from the electrical system one at a time to find what it is.
Dan you're right up to a point. Once he pulled all the fuses the circuit should have been open in 2 places. One at the battery and the other at the fuse panel. Since he metered 12.5v all the time he really didn't open the circuit by pulling the fuses. If he had it should read 0v just as if he had pulled the positive cable off the battery as well. There must still be another path through the circuit. The alt and reg are good suggestions. Make sure the battery is disconnected before disconnecting the alt or regulator.

Hank, you are 100% correct.


The fact that the meter shows the source voltage at that point means when the neg cable is reattached, some circuit is completed, somewhere. If all fuses, switches, etc, were open, you'd read 0V. Thus, battery voltage measured at that point does, indeed, indicate a drain, although it is impossible to measure how much the drain is by that method.

I was thinking more that using the voltmeter doesn't really tell you anything, when in fact, it does. The only thing an ammeter would tell you differently is the magnitude of the drain.