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New battery dead


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I put a new battery in my truck last week after the old one died, it was about 5 years old. Truck ran fine for a week then sat for 3 days. Went to start it and nothing; didnt crank, just dead. Where should I start? If it was a bad alternator I don't think it would have lasted a week. Nothing new done to truck, no new lights or anything.

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Something in the wiring is killing the battery. Unhook one of the bat cables. Charge the battery, Now touch the loose cable to it's post. There will be a spark. The brightness of the spark will be some indication of the drain. An amp meter will give an accurate indication. There will be a couple milliamps draw due to memory circuits but shouldn't be over 1/2 amp at most. With the amp meter still hooked up, remove one fuse at a time in the power distribution box. This will narrow down which circuit is defective. Don't overlook the possibility you got a defective battery. A simple test will determine if that is the case.

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You should start by determining if any circuit is drawing down the battery. I had an internal short in the radio recently drawing the battery down after 2-3 days of sitting. Use a multimeter on the 10A scale and connect it in series with the disconnected negative mains cable of the battery and the negative battery terminal. Look for any amp reading.

 

EDIT: Damn you Jim - UB FAST!

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That's correct, but you also have to observe polarity. The black (neg) meter lead goes to the battery neg terminal; the red (pos) meter lead goes to the disconnected mains cable. Current flow is through the meter using the 10A scale.

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cool, thank you. just cause i like to ask questions: if i put the postive meter lead (red) to the to the neg termianl, and the neg meter lead to the neg battery terminal would that make reverse polarity, and how would that affect the readings?

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  • 4 weeks later...

the battery in my 90 likes to fake being dead. the cables are old and not making a good connection to the terminals (yes, someday I might actually change them. maybe.). all I need to do is fiddle with it a bit and it fires right up.

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