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Old 09-12-2010, 12:33 AM   #27
mr48chev
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Join Date: Jul 2007
Location: Toppenish, WA
Posts: 15,705
Re: NEED HELP! I'm beyond aggravated

I agree with removing the negative cable and either using a multimeter or test light between it and ground to see if you have something drawing power when it shouldn't.

A blown diode in the alternator will cause a drain. This is usually caused by shorting something in the electrical system and getting a big spark in the process.

As someone said, an alternator that is overcharging will cook a battery in short order.
when running without anything on you should be charging right at 14.2 volts. If it is up around 15 or higher it is overcharging.

Is your alternator charging at all? You may be running on battery only and driving just far enough to run the battery down during your round trip. When you come out the next morning the battery is low enough that it won't crank the engine over.

Do a bit of homework and learn how to test a charging system correctly (it isn't that hard to do it right) rather than trying off the wall suggestions like checking for a spark and risking blowing a diode or worse. I cringe every time I see someone suggest some may or may not work or be correct method of testing electrical items because that's the way uncle Billy showed them on his Model A.
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