Jetta03

Hey all,

I have a 2010 5.4 and recently had some issues with the battery so I've replaced it. However in watching the new battery I'm seeing that the charge I see across the terminals with the truck off, doors closed, no lights seems low at about 12.2 volts. Charging with the truck running seems to vary between 14.0 and 14.3 depending on the driving situation.

So I have a request. Can anyone who drives similar truck daily go outside right now and measure the resting voltage across the terminals with a multimeter, making sure the doors are closed and all lights off.

And number 2, does anyone know what the charging voltage should be while driving?

Thx!

bubbabud

Your numbers are right on target the charging voltage will vary with the temperature and 12.2 is good for a battery depending on how long it's been sitting since it was last run

stormsearch

12.2v is bad, about 50% state of charge. They should be 12.6 - 12.7v with no load on them and sitting overnight. I think your problem is a drain on the system while engine is off. Charging voltage is fine.

Do you have any aftermarket electronic items installed?

sean453

go to napa or where ever and get them to load test your battery. I froze mine this winter so i had to buy a new one. your charging voltage is fine. if your battery on the load test is 80% or better i would just let it ride unless you live in a cold climate and you notice it turning over slow.

my two cents

Thislilfishy

Try a different multimeter. They aren't always that accurate, I have one that reads low about .5V here.


Ian

Rugger

A volt meter is a good thing to have. It doesn't need to be expensive to work. A $5 meter from Harbor Freight works well. The battery should be 12.8 or 9 at rest. Put your meter on it and have someone else start the truck. The meter should dip to even 9 or so and pop back up to 13.9 or so as the alternator recharges the battery from what was used to start the truck. It should then drop back down as the need for juice is taken over by the alternator. If the charging stays over 14 all the time, it will eventually fry the battery. Not good.
You may have dark current that is draining the battery. But, there may be an issue with the voltage regulator that is part of the alternator too.

stormsearch

Charging voltage is based on predicted battery temperature. The overall range of regulation is 13.3 - 14.7v. Given that he lives in Alberta, I bet his voltage doesn't fall below 14v very often.

The PCM commands the voltage control to the alternator. If the alternator does not follow it, the "Check Charging System" DTC is lit up.

Jetta03

Thx all. I do have voltmeter (how I measured the voltages in the first place, along with scanguage for running voltage). Checked this morning and found the key off draw is about 2 amps which would explain my problem. Time to start pulling fuses looking for the short.