Battery Drainage!

[awoodman]

I have an 85 s10 that i put a v8 into. i bought it with a v8 in it, swapped the engine, and rehooked all the wiring up. After about 3 days of not running, the truck will drain the battery. I did the trick I saw a lot of you guys do to try and trace the drain. I pulled the positive battery cable off and hooked a voltmeter up to it-the positive lead on the voltmeter to the positive batt. cable, and the negative lead on the voltmeter to the positive terminal on the battery. When the ignitions off, its reading 12 volts. This should mean there is a short somewhere draining the voltage. I pulled out every fuse in the box and nothing. So i went under the hood and started playing with stuff. On the back of my alternator, there is a stud to put wires on and a nut to tighten it. There are 3 wires on there. There is one that goes right to a plug on the side of the alternator, another that runs into the fuse box, and another that runs to the positive terminal of the battery. Does this seem right? When I disconnect the wire between the alternator and positive terminal of battery, the voltage drops all the way to 0.09v. This is leading me to think that that cable isn't in the right place. Is it? What does an alternator usually connect to? I hope you can help. Thanks for any input!

[oncearacer52]

You are supposed to put the meter or test light between the battery and the NEG. cable. If it lights up or shows voltage then start pulling fuses until the light goes out. That will isolate the short. Of course do all this with the key off. But like you say you could have some wiring problems.

[Scotty_S-15]

Normally there is just one wire going to that stud...... but looks like someone else decided to use that as a junction point, maybe, instead of the starter positive terminal, or the firewall junction block. But if that is the case, it isn't necessarily the cause of the problem. My guess would be that the field in the alternator is constantly energized, causing the drain. And no, one wire shouldn't be jumpered back to the alternator plug. Some guys do that, ( the voltage sensing wire) and while it isn't exactly right, it will work. I'm thinking it's jumpered to the wrong side of the plug, maybe to the field side of the plug. Constant voltage there will cause a drain. Any chance the alternator is slightly warm?

Oh, and BTW, to find out if the above IS the problem, just unplugging the alternator plug should stop the drain.:icon_wink:
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