my voltage is incredibly low (8) and every once in a while it jumps to 13. when its below 13 , my car squeaks as if the belts are loose, when its at 13, it completely fine. is this because i need a new alternator and that;s it? or is it a combination of things?

 

If your voltage is 8, you need a new battery too.

I assume you've checked to see if your belts are actually squeaking? Try rubbing the wheels (for want of a better word) where the belt goes with some sand paper to rough them up a bit.

A good alternator will be charging between 13.5 and 15 volts. Less than 13.5 and it's useless. Any more than 15 and you'll fry your battery.

When (if) you replace the alternator, you may as well spend an extra couple of bucks and replace the belt too.

Si

 

the battery is only 4 months old, so its not the battery. All the belts are fine. it's just very suspicious to see that the voltage and the squeeking is synchornized (sp?).

 

If you had said your voltage was 12, I'd agree. Placing a multimeter across the battery terminals and getting a reading of 8 volts means that the battery does not have a potential difference of 12v. It doesn't matter how old it is. Try removing it from the car and charging it for an hour. If you still get a reading of 8v then get your battery warranty out.

If you're getting a reading of 8v when the engine is running, then the alternator is either not putting out a charge, or not getting driven sufficiently to produce a charge. That can only be the alternator itself at fault, or the drive belt. Get the alternator to a shop and get it bench tested. You say the voltage jumps to 13 every so often. Without seeing the car for myself, this says to me that the belt is slipping for a while, heating up, gaining grip and spinning the alternator for a while until it cools, loses it's friction properties and releases. That's just experience talking though.

Si

 

sorry, i was mistaken in stating my problem. first, the voltage isn't at 8, its just above the yellow bar..... that looks to be about 10ish. also, i noticed that the squeaking only occurs when the headlights are up, not when driving during the day. any help on this?

 

Loose belt. Lights on = more load on the alternator. Enough to make the belt slip. If it's been loose long enough(or just plain old) you will have to replace it.

 

If it were me (and it has been) I wouldn't trust the in-car volt meter. I would put a multimeter across the battery terminals.

82camaro is correct when he states that the headlights put more load on the alternator. Belts can become glazed and slip sometimes, and sometimes they only slip at certain loads.

Si

 

I had a similar problem with my alternater making that same squeaking noise and getting low voltage from my battery. Turns out that my belt was splitting in half so I was never recharging my battery fully. Brought a new gatorback belt all is fine now. Better check your alternator too.