was driving home the other day,and my voltage was reading about 14 or 15,lot higher than usual,usualy stays just over 12. next day my voltage stays about halfway between 0 and twelve,and when i rev it goes to twelve.but goes back down after a few minutes.sometimes itll stay at 13 for a few,but if i mess with the heat/radio brakes,and healights,it goes back down.i have a brand new battery and i made sure i had good connections.is it the alternator?

 

I think so........similar thing happened to me when my alternator got wet......if you can take to a pplace where they can do a charging system test.....it's Kragen's here but I know it's called something elses in other places...

 

Take your car to Auto Zone, Checkers, whatever...Have them diag your charging system, they do it for free.

 

coool thanks a lot,sucks,cause itll hardly start my car here .its like 5 below zero right now.friggin thing. when i first start it up,itll stay at 12,but when i turn **** on and start to move it drops to like 5 or so.

 

anything under 12.6 volts and you are running on the battery and the alt is dead or disconnected.

The ECU won't run on anything under 7 volts.

So if the car is running, and your meter is only saying 5 volts, you have a bad connection at the back of your gauges.

 

it should be at 14 when driving. anything under 12-13 is very bad.

 

Yea sounds like alt but Mark is right also, your gauge could have a bad hookup. Good luck man!

 

i tested the battery with the car started with a volt tester. it came to like 11.3 to 11.7,i had a good connection with the battery and tester. i dont think the guage connections are bad.it looks like even when its low its right around 7-8. i started noticing the interior lights would dim when i would turn my radio on,im just going to go to autozone and get that test.thanks. (edit)i also noticed my heater blower isnt very strong.i know its prolly the alt.but i was just wierded out by the guage jumping up really high yesterday actually, if normal voltage under driving is around 14,the it jumped up to normal,ha

 

11.3 means you have a bad cell in the battery and it will need to be replaced, that is with the car not running, or not even with the key on.

If that is with the car running, your alt is bad or disconnected.

Sure sounds like you also have a corroded gauge screw on the back of the cluster. That would explain the intermittent gauge operation.

 

my car has the similar problem , I have a new battery , alternator, when I test the battery it has 11.5v-11.9v.
when I drive the car at day time , my volt meter show 11.5v-13.7v, night time it only shows 11.3v-12.5v. and only 10.9 at idle.

 

It sounds like your 3 year old battery is near the end its days.

I would check the alternator & the primary cables also.

 

Make sure your alt. belt is at the correct tension. They will loosen up after a few miles after install as well I lost mine the other night.

Pat