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We inherited a 2003 Ford F150 4.6 liter V8 with only 55k miles on it.
Nice truck and I'd like to keep it but recently I changed the battery and found that the new battery is now dead. So it seems like a short somewhere. How do I go about finding a short in the wiring? I've heard that mice can eat insulation off wires, would that cause a short that would completely drain a new battery?
Yes, rodents can/will eat wires. However, let me ask this....Is there a light on the back of the cab, that shines into the bed? If so, are you sure it's off? I say this because I was walking through a parking lot, a couple of days ago, and saw a truck with this light on. It was the middle of the day, so it wasn't readily visible to the truck's owner, therefore it was left on.
Probabilities are high it's the alternator. Ford uses what some like to call a final diode in the alternator to stop current from going back into the alternator when the key is in the off position. You could call it a controlled short. Taking the alternator to a parts house for testing tells you nothing since all they check is for output. NO rebuilder checks the diode for failure so buying a rebuilt alternator for a Ford is usually nothing but changing one bad alternator for another bad alternator. You have to buy a NEW alternator to fix the problem.
If you are mechanically inclined, you can easily test the alternator for a bad diode. Find the large wire coming out of the alternator. Careful as it is wired directly to the battery. Carefully remove the wire from the alternator. If you see any current jumping from the wire to the alternator post, any small sparks at all, the diode is bad. The battery must have a charge and be connected via the battery cable for the test but no key required in the ignition.
Thanks for the ideas. I'm going to see about acquiring a multimeter to see if I have a parasitic drain somewhere. I'm kinda surprised that a brand new battery can completely drain that quickly but I guess it can.
If you have a highly sensitive, highly accurate voltmeter with a millivolt range.........just check for
voltage-drops across your fuses. The circuits with no shorts should all have the same voltage-drops across the fuse....the circuit that is improperly drawing current should have a higher voltage-drop across the fuse than the good circuits. Of course you have to know which circuits have power flowing to them when the key is off.
Closing the door may not be fully depressing the interior dome-light switch. Try turning the dome light off with the 3-way manual switch. Or at least, check visually and make sore it goes off when closing the door.
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