Battery Light On - Please Help
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Senior User
Joined: Dec 2010
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Battery Light On - Please Help
My son's '98 F-150, 4.6 2WD is having electrical trouble, and I cannot trace it down using normal methods. For the record, I rewired my '66 F-100 for a later alternator, so I understand electrical techniques and work, but this is driving us up the wall.
The battery light stays on, but some charging must be occuring as it took 2 months for the battery to run down, with daily driving. Testing by Advance Auto with the alternator on the truck seems to indicate they are both functioning normally. The alternator was replaced with a new one (not rebuilt) about 8 months ago, and has been working fine until the light came on.
All fuses are good. All connections seem to be good, no corrosion, broken wires, etc. Initial continuity checks seem to show there are no wires broken internally.
Any ideas? Does the computer get involved in any of this? I really appreciate any help you can give us.
The battery light stays on, but some charging must be occuring as it took 2 months for the battery to run down, with daily driving. Testing by Advance Auto with the alternator on the truck seems to indicate they are both functioning normally. The alternator was replaced with a new one (not rebuilt) about 8 months ago, and has been working fine until the light came on.
All fuses are good. All connections seem to be good, no corrosion, broken wires, etc. Initial continuity checks seem to show there are no wires broken internally.
Any ideas? Does the computer get involved in any of this? I really appreciate any help you can give us.
Senior User
Joined: Jun 2010
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Check: Idler Pulley, Tensioner Assembly, Belt for stretching, cracking, and oil, and I bet if you bought that alternator aftermarket it has a limited lifetime warranty if so I would just replace it again. Only simple thing i can think of is the alt has a diode staying open until a laod is put on it.
Hotshot
Joined: Jul 2005
Posts: 11,932
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alternator should put out about 14.5 volts or so when charging. If your getting lets say 12.5, you can keep the battery charged up if you run long distances, but it will go dead on short runs, long idle time, etc.... check with a volt meter across terminals with truck ideling.... it is alos ppossible that battery or alternator went bad in 8 months-- check the voltage to make sure... recharge battery, then check every couple days after driving, if it checks o.k. today.
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