High voltage (18+ on console) - F150online Forums



High voltage (18+ on console)

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Old 03-09-2012, 12:19 PM
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High voltage (18+ on console)

Was going to work today, and my battery light and voltage indicates 18 + volts on my truck. Just replaced the alternator on my truck in December. Does anyone know if revving the engine RPMs high would blow a regulator on the alternator? I was behind some lost, old dude on the cell phone, and revved my engine to 4 - 5 k rpms, and then my battery light came on. I live in Denver, and traffic sucks everyday, we are like Little LA here.
Also, will I fry my electronics if I drive home today with a high voltage reading?



98' F150 (4.6 L, manual tranny).
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Old 03-09-2012, 12:36 PM
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Revving engines will not damage the alternator, that is the whole idea of the regulator. Though if you replaced your OEM alt with a junk one, might not live up to the same standards. Personally, anything over 16v and things can start to get hairy. Requirements for modules to normally operate is between 9 - 16v. You might not damage anything, but just about every module will shut down, pull a DTC.
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Old 03-09-2012, 06:10 PM
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now normal

Just checked before I went home and now the battery light is not on, and the charge indicator is in the normal range. Is there anyway that the battery could be going out? The battery is reading at 11.7 V not running, and when running the battery reading is 15.2 V. Seems like a low battery.

I have never heard of a battery going dead while being driven, unless the alternator goes out. Anybody heard of that?

I do recall the old dude I high tailed it by looked like George Burns, smoking a cigar. Maybe he had something to do with it.
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Old 03-09-2012, 11:10 PM
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Check battery voltage under starting load. If it drops below 10.5 volts you have a bad cell.
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Old 03-10-2012, 12:35 PM
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Quote:
Originally Posted by Tat2ski View Post
Just checked before I went home and now the battery light is not on, and the charge indicator is in the normal range. Is there anyway that the battery could be going out? The battery is reading at 11.7 V not running, and when running the battery reading is 15.2 V. Seems like a low battery.

I have never heard of a battery going dead while being driven, unless the alternator goes out. Anybody heard of that?

I do recall the old dude I high tailed it by looked like George Burns, smoking a cigar. Maybe he had something to do with it.
11.7V no load sounds like a badly discharged battery to me. I think you should have it load tested.

- Jack
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Old 03-13-2012, 12:09 PM
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follow up

A follow up to last Friday, I ended up needing a jump to get home, and my alternator was trying to charge the battery at 18.5 Volts when I checked.
Went and got a new battery, and installed it, but the alternator was still charging at 18 + volts. I guess I must have fryed my alternator on the way home trying to charge a shot battery. The alternator was only 3 months old, and I guess the regulator got fryed. It was under warranty at Pepboys.
Would any alternator fry (regulator fryed) by charging a dead battery?
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Old 03-13-2012, 12:53 PM
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A dead battery does not cause the alternator to put out +18v directly. Indirectly trying to re-charge a battery and accidentally hooking up the leads backwards can damage the alternator.

At +18v, you likely boiled the battery way over-charging it.
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Old 03-13-2012, 05:13 PM
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Quote:
Originally Posted by Tat2ski View Post
A follow up to last Friday, I ended up needing a jump to get home, and my alternator was trying to charge the battery at 18.5 Volts when I checked.
Went and got a new battery, and installed it, but the alternator was still charging at 18 + volts. I guess I must have fryed my alternator on the way home trying to charge a shot battery. The alternator was only 3 months old, and I guess the regulator got fryed. It was under warranty at Pepboys.
Would any alternator fry (regulator fryed) by charging a dead battery?
Seems to me that the problem would be the voltage regulator, not the alt.

The alternator is supplying high voltage to charge the battery and the voltage regulator isn't lowering the alternator's voltage to the battery's requirements.
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