Battery/charging issue?
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Battery/charging issue?
This past February I had the battery and alternator replaced on my '95 LWB 4.0 (about 270k miles). The mechanic found the wiring harness to the alternator had been pinched underneath it, so he repaired it.
Now the vehicle will crank but not start. The voltmeter sits at the left edge of the "O" in Normal. Attaching a 10-amp charger brings the battery to 12.83 volts when the charger finishes (less than half an hour). Then the voltage looks like this:
key off - 12.83
key on - 12.43
key on, headlights on - 12.05
(when lights left on about a minute)
key on, headlights off - 12.28
key off - 12.43
So about a minute of headlights knocks .4 volts off a "charged" eight-month-old battery which started at 12.83 (it's an Autocraft Silver 65-1).
Several times in the last couple of weeks the voltmeter would drop momentarily while the engine was running, then come back up. With the benefit of hindsight, I now wonder if the alternator (a remanufactured unit) was saying goodbye and has taken the battery with it...
Now the vehicle will crank but not start. The voltmeter sits at the left edge of the "O" in Normal. Attaching a 10-amp charger brings the battery to 12.83 volts when the charger finishes (less than half an hour). Then the voltage looks like this:
key off - 12.83
key on - 12.43
key on, headlights on - 12.05
(when lights left on about a minute)
key on, headlights off - 12.28
key off - 12.43
So about a minute of headlights knocks .4 volts off a "charged" eight-month-old battery which started at 12.83 (it's an Autocraft Silver 65-1).
Several times in the last couple of weeks the voltmeter would drop momentarily while the engine was running, then come back up. With the benefit of hindsight, I now wonder if the alternator (a remanufactured unit) was saying goodbye and has taken the battery with it...
Post Fiend
Joined: Oct 2005
Posts: 5,242
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From: Kiev, Ukraine
first step - check connectors and wiring, then check voltage supply of vltage regulator (as I remeber 3 pins: ign.on, D+ and ground). If you are sure it is OK, pull out it with brushes, replace them if you see they are worn, check contact rings, clean them, measure rotor resistance...
Elder User
Joined: Dec 2006
Posts: 830
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From: Kitchener,Ontario,Canada
If engine cranks fast enough it should start whether or not the alternator is bad...... is the crank speed too slow?
Sounds like battery is O.K. clean the battery terminals just incase. Voltmeter needle dropping like that while running is not normal. You may have a dodgy alternator I would get it load tested. Normal charging voltage with engine running at idle is 14-15volts not more or less, but you still need the load test to see if the alternator is able to generate full output,
In spite of that I would not be surprised if you have another problem which is preventing the engine starting! Will it start if you connect a jumper battery?
Sounds like battery is O.K. clean the battery terminals just incase. Voltmeter needle dropping like that while running is not normal. You may have a dodgy alternator I would get it load tested. Normal charging voltage with engine running at idle is 14-15volts not more or less, but you still need the load test to see if the alternator is able to generate full output,
In spite of that I would not be surprised if you have another problem which is preventing the engine starting! Will it start if you connect a jumper battery?
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