I have a 93' 240 which looses battery when running. Both the alternator (new) and battery (year +) test good at autozone. I have replaced the alternator ground wire. W/o running, charged battery reads about 12.9 volts it immediately DROPS to just over 12 volts when running with nothing turned on. Battery light illuminates on the dash as it should. I removed the small red wire to the alternator and have 12V there. When I rev the engine, the voltage drops more. I've checked everything I know to check - any suggestions???