Battery discharge!

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Jul 11, 2009 | 12:14 PM

recyclemor

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Battery discharge!

Battery discharges overnight. Have disconnected alt and have a draw of 8.5 volts off neg post. Found if I disconnect one of the yellow wires off the start solenoid positive side have no draw. Looking for circuit diagram for wiring.

Jul 11, 2009 | 12:41 PM

Lazy K

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Connect your meter again and start pulling fuses, that may help to isolate the fault.
Can`t help on the wiring diagram but it would help those that could if you included year/model/engine of the truck.

Jul 11, 2009 | 12:45 PM

DBGrif91

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From: Des Moines

How old is the battery? Try completely unhooking the battery, giving it a full charge, and then see what it's reading. Anything less than 12 volts and it's dead.

Jul 11, 2009 | 01:04 PM

jr32560

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From: southern md

Quote:

Originally Posted by Lazy K

yup I'm with this post 100%-that way ya can try to isolate where the drain is coming from-just pull one fuse at a time and check to see which circuit is draining the battery

Jul 11, 2009 | 01:27 PM

recyclemor

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1990 f-150 4.9 L. New battery. Pulled all fuses no change. Meter hooked to neg side battery post to unhooked neg. cable. Shows 8.5 volt draw.

Jul 11, 2009 | 01:45 PM

rainbowATF

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From: Elyria, Ohio

Check your battery cables. I replaced my ground and the clamp on my positive. The positive wire looked new. I found that the positive at the starter had the insulation deteriorated from heat (?) back abount 3 inches. The bare wire was green. Apparently moisture created ground path to drain battery. I replaced the cable and battery holds charge and starter cranks like new.

Jul 11, 2009 | 02:19 PM

jroehl

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From: Lafayette, IN

Quote:

Originally Posted by recyclemor

1990 f-150 4.9 L. New battery. Pulled all fuses no change. Meter hooked to neg side battery post to unhooked neg. cable. Shows 8.5 volt draw.

This means nothing.

You need to use an ammeter between the negative post and cable to measure for a drain on the battery. You shouldn't have more than a couple hundred MILLIAMPS of draw. You'll need to pull the bulb for your underhood light, or have someone hold in the switch, everything needs to be off.

Also,

1. What is the voltage on the battery after charging it overnight?
2. What is the voltage on the battery with the vehicle running?
3. Pop off the vent caps on the battery (vehicle not running). There should be six holes with acid showing. Working from one side to the other, stick your voltmeter probes into adjacent holes and measure the voltages (i.e., 1-2, 2-3, 3-4, 4-5, 5-6). They should all measure about 2.1V or more.

Jason