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Old 06-20-2018, 01:57 PM   #2
Msgt USAF Ret
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Join Date: Jan 2005
Location: Kalamazoo, Michigan
Posts: 8,274
Re: Alternator draining battery?

Check the 1 and 2 pin wires to be sure they aren't reversed. IF the key is off the 1 pin wire will not have voltage, and when it is turned on,the wire should have 12 volts. The 2 pin wire should be hot all the time.l If they are correct then the alternator diodes could be shorted to ground and will drain the battery over time.

Sometimes the engine will continue to run with the key off when the two wires are switched.

I'll check one of my SI alternators and see what readings I get on the no. 2 connection between it and ground and then reverse the leads on the meter and see if I get a reading to see if it's flowing both ways.

metallic green 67 stepside
74 corvette convertible
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1995 Harley wide glide

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