1967 Oldsmobile 442 V8 Two Wheel Drive Automatic 95000 miles
Battery slowly drains (48plus hours). Even with ground side of battery removed. Even with all fuses inside car removed. Remove battery positive terminal and battery maintains 100% charge for over three days. When running car battery is charged to 100%. Car parked for 8 hours its down 10-20%. Fusible link removed and inline 40 amp bayonet maxi fuse and holder installed. Pulled alternator, went to local starter/generator shop. They say it tested good. Get a second opinion? Unplugged horns at the relay (on fenderwell junction block) Car starts and runs good. All accessories and lights work good with the exception of the back-up lights which are unplugged. Car is matching number 400ci/TH400, PS, PB, Air, AM radio. No other aftermarket accessories added. No cooling fans, etc.
Have you tried unplugging the voltage regulator? Sounds like there arent too many things left to try, but the charging system is the only thing that is connected to the pos cable that could do that. Really odd it does it with neg cable off. The horn relay in that vehicle is major power junction as well, try disconnecting it if the regulator doesnt do it
May, 8, 2010 AT 9:03 AM
Get an analog voltmeter remove the negative battery cable, attach the Black lead to the battery post, Red lead to cable end, then pull fuses one at a time, make sure there are no accessories or lights in the on position, Key off! Close the door have someone in the car, pull fuses one at a time after each fuse check meter, when you pull the fuse for the bad curcuit, the meter will drop to 1 volt or so. Check all fuses, even under the hood. If meter does not drop, remove the battery connection from the alternator, if it drops now, the diodes are bad in the alternator. Put the fuse back in were it goes as you go so you don't forget which fuse goes were! Wait several minutes after hooking up the meter before pulling fuses, test with a good battery! http://www.2carpros.com/first_things/why_is_my_car_battery_dead_over_night.htm
On yours you dont need to wait, that's for newer cars with central timers..