battery light
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New User
Joined: Mar 2005
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battery light
I did a throttle body cleanup and now my battery light comes on I cleaned the battery cables and looked for disconnected wires and didnt find any, this is a base truck with a 5.4 v8 and automatic with ac no other options. The battery test out ok with a load tester and it doesnt act like it has a low battery and runs fine. Thanks for help. It is a 99 f150 long bed.
James
James
Lead Driver
Joined: Sep 2006
Posts: 7,907
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Check for charging by using a voltmeter accross the battery while the engine is running after a start up.
You should see a voltage in the range of 15 that tapers down as the charge is being replaced into the battery.
If you don't see this, it's alternator time. Have it tested.
You should see a voltage in the range of 15 that tapers down as the charge is being replaced into the battery.
If you don't see this, it's alternator time. Have it tested.
Postmaster
Joined: Nov 2006
Posts: 4,517
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From: SE Wyoming
With the engine anywhere above about 800rpm you should have 14.3-14.6V constantly, It should be about the same at idle, I have Ud pulleys so mine isn't I don't know what it was at idle stock, but I am pretty sure it should still be 14.3 range.
All that said the B. light is tied to the Alternator, when mine started flashing my alt. was bad within a few hours of driving.
All that said the B. light is tied to the Alternator, when mine started flashing my alt. was bad within a few hours of driving.
Freshman User
Joined: Nov 2006
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My battery light came on only under high RPM's like when i was passing someone, so i checked my alternator with every test there is that i know of, ( all of the ones mentioned above in the other posts ) and my alternator tested fine, but i changed it anyway and the problem was fixed. Also when i took off the alternator and i spun it by hand, u could hear a grinding time noise, the bearing where starting to go bad and it would have only been a matter of time b4 it left me.
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Lead Driver
Joined: Sep 2006
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fourwheelin,
the normal testing done can't duplicate worn brushes and out of round commutator that begins to float the brushes at hi rpm, causes arcing and erroded the parts even faster.
With poor contact, the charging gets erratic and the voltage regulator does funny things with these conditions, with the red light the final result.
the normal testing done can't duplicate worn brushes and out of round commutator that begins to float the brushes at hi rpm, causes arcing and erroded the parts even faster.
With poor contact, the charging gets erratic and the voltage regulator does funny things with these conditions, with the red light the final result.
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New User
Joined: Jul 2006
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From: Stockbridge, Ga.
Originally Posted by fourwheelin
My battery light came on only under high RPM's like when i was passing someone, so i checked my alternator with every test there is that i know of, ( all of the ones mentioned above in the other posts ) and my alternator tested fine, but i changed it anyway and the problem was fixed. Also when i took off the alternator and i spun it by hand, u could hear a grinding time noise, the bearing where starting to go bad and it would have only been a matter of time b4 it left me.
that happen to me too.I bought my wife this 01 F150 a year ago and when I was test driving it the battery light came on at high RPMs so I was like **** but she like the truck so much that we went ahead and bought it.
The alternator went out last night.... I'm replacing it tonight the truck made it home and then it did not crank up, I jump started and massure the Voltage and I was getting 8.5 volts nothing worked like: Horn, interior/exterior lights, windows but the engine keep runnig at least for another 10 minutes and then it die on my way to Autozone to get the alternator check. lol