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driving voltage

nat3d

Wait, I don't drive a civic anymore....
VIP Member
3,335
1,566
Adams MA
Vehicle Model
Ford Focus ST
Body Style
Hatch
hey guys i have a voltmeter and as im driving ive noticed that on ocasion rather than run at 14.3v my car has been running at 12.5v and when it first started it was only when i was on the gas it would drop to that but now it seems constant (as of my drive home) whats going on?
 

ADExternal

Lvl: 99 Modifier
1,917
1,535
Houston, Tx
Vehicle Model
Civic Ex
Body Style
Coupe
I got you @nat3d .

A car alternator needs to be putting out at least 13-14 volts (ideally between 13.8 and 14.2 volts) to effectively charge a 12 volt car battery. If the alternator is putting out too much voltage (15+ volts), it is likely your battery acid will boil over out of the battery. On the other hand, if its constantly at 14v than your battery isnt holding its charge or its losing charge somewhere in your system very fast.

As long as its between 13-14 volts, your alternator is working fine. So its just the battery at this point.
 

nat3d

Wait, I don't drive a civic anymore....
VIP Member
3,335
1,566
Adams MA
Vehicle Model
Ford Focus ST
Body Style
Hatch
I got you @nat3d .

A car alternator needs to be putting out at least 13-14 volts (ideally between 13.8 and 14.2 volts) to effectively charge a 12 volt car battery. If the alternator is putting out too much voltage (15+ volts), it is likely your battery acid will boil over out of the battery. On the other hand, if its constantly at 14v than your battery isnt holding its charge or its losing charge somewhere in your system very fast.

As long as its between 13-14 volts, your alternator is working fine. So its just the battery at this point.
its been sitting at 12.something though :/
 

Monk

Well-Known Member
4,218
2,196
SW Virginia
Vehicle Model
2012 Civic EX
Body Style
Coupe FG3:ASM
i have a volt meter wired
If it isn't wired directly to the batt you're going to get a lower reading than what the batt is actually doing.
 

the insider

Well-Known Member
309
253
north of the 49th, south of the 401
Vehicle Model
civic si
Body Style
sedan
The charging system on the newer Civics don't work like they have traditionally - there will be times when you are driving that the alternator will not be charging. The charging protocol has been changed to improve economy.
 

Chuckable

Well-Known Member
86
34
the insider is correct, at least for Si models. Others, I have no idea. Try turning on your headlights. Your voltage should increase. If not, I'd take it to the dealer.
 
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