Battery light coming on
12-02-2016, 03:01 PM
#2
Senior Member
What have you done so far ?
12-02-2016, 03:45 PM
#4
Senior Member
Check the alt fuse, it's an inline fuse that can become loose in the holder. Bat light comes on when it looses connection. Other than that, you'll need to check the alt itself or have it checked along with the battery.
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2001f150hd (12-02-2016)
12-02-2016, 05:11 PM
#5
Senior Member
Definitely check all fuses for contact and burnout that is associated with the alternator.
If you don't have an owner's manual you can download one from Ford's website. The fuses are page 206-213 (I have an '02 F-150) for both power control box (under the hood) and main fuse panel. You're going to have to register your VIN number, which is cool as you can also find any recalls if they exist.
If your fuses all check out and the problem still exists, check the belt and idler pullies for wear or play. The pullies should spin freely yet feel securely attached to the enging. If they feel sloppy and/or the belt is missing any ribs, shows signs of wear, replace them. Those will cause slipping which results in slower revolution on the alternator and cause it to undercharge. Thus the battery light comes on.
Auto Zone, O'Reilly's and Advanced Auto Parts will all check your alternator for free. Checking all of that is much less expensive than replacing the alternator right off the bat.
If you don't have an owner's manual you can download one from Ford's website. The fuses are page 206-213 (I have an '02 F-150) for both power control box (under the hood) and main fuse panel. You're going to have to register your VIN number, which is cool as you can also find any recalls if they exist.
If your fuses all check out and the problem still exists, check the belt and idler pullies for wear or play. The pullies should spin freely yet feel securely attached to the enging. If they feel sloppy and/or the belt is missing any ribs, shows signs of wear, replace them. Those will cause slipping which results in slower revolution on the alternator and cause it to undercharge. Thus the battery light comes on.
Auto Zone, O'Reilly's and Advanced Auto Parts will all check your alternator for free. Checking all of that is much less expensive than replacing the alternator right off the bat.
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2001f150hd (12-02-2016)
12-04-2016, 01:49 PM
#6
Senior Member
Forgot to mention check the belt tension pulley too. It's spring loaded and if it becomes weak or breaks you're still going to have some belt tension but not enough to drive the alternator correctly...or the waterpump, a/c compressor or crank shaft at the speed it should.
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2001f150hd (12-05-2016)
12-04-2016, 02:06 PM
#7
Cycle For Fun and Health
Rev the engine slowly and see if the light comes on at a certain RPM time after time.
This would indicate the alternator bearings and or brushes are going bad.
Mine started like that at just over 2500 RPM and then got progressively lower over a period of time. When the light began coming on just over 2000 RPM, I replaced the alternator. If you travel distances and or unexpected places, need to repair almost immediately.
I was always close to home so not worried about complete failure.
This would indicate the alternator bearings and or brushes are going bad.
Mine started like that at just over 2500 RPM and then got progressively lower over a period of time. When the light began coming on just over 2000 RPM, I replaced the alternator. If you travel distances and or unexpected places, need to repair almost immediately.
I was always close to home so not worried about complete failure.
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2001f150hd (12-05-2016)
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12-04-2016, 08:24 PM
#8
Super Moderator
Rev the engine slowly and see if the light comes on at a certain RPM time after time.
This would indicate the alternator bearings and or brushes are going bad.
Mine started like that at just over 2500 RPM and then got progressively lower over a period of time. When the light began coming on just over 2000 RPM, I replaced the alternator. If you travel distances and or unexpected places, need to repair almost immediately.
I was always close to home so not worried about complete failure.
This would indicate the alternator bearings and or brushes are going bad.
Mine started like that at just over 2500 RPM and then got progressively lower over a period of time. When the light began coming on just over 2000 RPM, I replaced the alternator. If you travel distances and or unexpected places, need to repair almost immediately.
I was always close to home so not worried about complete failure.
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2001f150hd (12-05-2016)
12-05-2016, 01:40 AM
#9
It's possible for the international regulator to be going out. I had this problem before and it was the alternator have your charging system looked at alt,battery,cables....
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2001f150hd (12-05-2016)
12-05-2016, 09:43 AM
#10
Senior Member
I've had this happen before on my Ranger. It was a bad voltage regulator/bad brushes.
With the engine running, put a volt meter on the battery. Idling, you should be seeing 13.5 to 14.5 volts. Have someone rev the engine up to 2500-3000 RPM and watch the meter. If it drops to 12 volts (or less) or rises above 16 volts, the voltage regulator or brushes inside the alternator are bad. It is a replaceable item, but you usually need to hit up an alternator/starter rebuild shop to source the parts.
With the engine running, put a volt meter on the battery. Idling, you should be seeing 13.5 to 14.5 volts. Have someone rev the engine up to 2500-3000 RPM and watch the meter. If it drops to 12 volts (or less) or rises above 16 volts, the voltage regulator or brushes inside the alternator are bad. It is a replaceable item, but you usually need to hit up an alternator/starter rebuild shop to source the parts.
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2001f150hd (12-05-2016)
