System voltage a bit low? | Ford Explorer Forums - Serious Explorations

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System voltage a bit low?


July 1, 2015
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Year, Model & Trim Level
03 Ford Explorer Sport Tr
I have had this 03 Sport Trac for about 3 years. The voltage gauge has always been reading a little under half. I have a good meter and voltage at idle and higher reads 13.8v to 13.9v.

A few days ago my alternator died. I replaced with a used one and system voltage still the same.

Should it not be 14-14. 2v? Is 13.8 sufficient?

What else could be wrong?


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Did you take the reading when it was first started & cold or when the engine warmed up? Internal voltage regulators will decrease the charge when it gets hot. I've read about some new systems which use PWM providing under 14 volts since it monitors the battery's load more precisely, and only provides what is needed to run without overcharging. Some AGM batteries don't need a large charge to keep them running since they accept a charge faster.

13.9v isn’t unreasonable.

My scangauge reads between 13.8 and 14.4 depending on the truck's mood I guess. I too thought the 13.8 was low and threw on a new alternator, fired it up and it still read 13.8 on that day, engine running no accessories were turned on at the time. Go figure

13.8V seems pretty good. I wouldn't be concerned about it, though any time I've checked my voltage at the battery (idling no accessories on) I typically see readings in the low-mid 14's. It may depend on the outside temp and the voltage of the battery. The voltage regulator works as a balancing act between the alternator and the battery, trying to keep it charged w/out over charging it.

Thanks for the response folks, I feel better about it now.