Dead battery on my 2002 GMC pickup

PRJ

Well-Known Member
The battery on my 2002 GMC pickup was dead this morning such that the electric door locks wouldn't even unlock. The battery in it is less than a year old, so I connected it to a battery charger and seems to be taking a charge.

Since a dead battery has never happened on this truck before, I disconnected the B+ wire from the alternator and connected an ammeter between the B+ wire and the B+ terminal on the alternator and measured a current draw of 0.04 milliamps. I'm thinking that the current draw at the B+ post should be zero.

Do you guys think that I could have a defective alternator where the internal diodes are bad????
 

nitehawk55

Well-Known Member
Jan 28, 2014
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Always some parasitic draw on the battery , I would say yours is normal .

If the battery has gone dead after only one year I would suspect one of the cells has shorted out or your charging system isn't working .
 

8433jeff

Capt. Sunshine
Jul 31, 2013
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Without unhooking the negative terminal, you are still sending current to the computer clock and radio. And a year is more than enough time to draw it down.

Once you get down to around 9-10 volts I'm told the computer will start tripping relays and stuff, hastening the current draw.
 
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nitehawk55

Well-Known Member
Jan 28, 2014
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SW Ontario
Without unhooking the negative terminal, you are still sending current to the computer clock and radio. And a year is more than enough time to draw it down.

Once you get down to around 9-10 volts I'm told the computer will start tripping relays and stuff, hastening the current draw.
The truck didn't sit for a year , the battery was only 1 year old .