Alternator going bad?

[slavrenz]

So I've noticed that over the last few weeks, my headlights have been dimming periodically while I drive. The dimming is not very noticeable, but it is noticeable enough to bother me.

I finally plugged in a voltage tester while driving tonight, and saw that my alternator voltage was dropping from about 14.3V to about 12.8V while this dimming occurred. Does this mean my alternator is going bad? I have inspected the physical connections on my alternator (and have cleaned the connections on my battery), and everything looks good.

Any suggestions?

 

[CheeseHelmet]

How tight is the alternator belt? Mine was doing the same thing (and squealing occasionally) until I tightened it and haven't had a problem ever since.

 

[carter1551]

my brand new alternator did the same thing. Granted I do have an underdrive pulley so im probably not getting as much juice as everyone else. It sits between 13.9-14.1 most of the time but occasionally it drops back down in the 12's for a quick second or two and goes right back up. My alternator has been doing this since I installed it about 6 months ago.

Hope that helps a little bit

 

[slavrenz]

How tight is the alternator belt? Mine was doing the same thing (and squealing occasionally) until I tightened it and haven't had a problem ever since.

i have noticed my belt squealing sometimes when I start 'er up in the mornings.

i'll try tightening the belts first and see what that does.

 

[Khemraj]

well i have a similar problem except it's not the alternator, the belt shredded to pieces last night on me and the serpentine belt is frayed pretty bad at 75k...is this normal?

 

[MP5_Joe]

check your belts. I'm at 102,000km (around 65,000 miles) and had to do both my belts cuz the alternator belt decided to give out.

 

[JReichle1]

Any alternator that is in good condition should give at least 13-14 volts when charging with the headlights on. If the reading dips into the 12v range the alt is not charging properly. First I would check the tension on the belt. I usually tighten the belt till you can almost play it like a guitar string. If you tighten the belt and check the charging with the a/c and the headlights on and the reading dips into the 12's the alternator is probably going bad. Good luck. I would caution you to get a new alternator as opposed to a remanufactured unit. Even a good oe part from the junkyard is better than most remanned units.

 

[richs970]

I just recently had to replace my alternator at 65k miles too. If you hear that squealing it usually means that the belt needs tightening or needs to be replaced. I actually had some squealing today because my new belt is stretching out a bit - I tightened the belt up and the squealing is gone.
Not sure about the voltage, but fixing the belt may help the alternator pully spin at it's intended speed?? Might as well try the belt before pulling the alternator right? A belt is only a couple bucks and 10 minutes of work.

 

[slavrenz]

well i have a similar problem except it's not the alternator, the belt shredded to pieces last night on me and the serpentine belt is frayed pretty bad at 75k...is this normal?

Is it normal for your belt to shred to pieces? Um...no.

 

[richs970]

Is it normal for your belt to shred to pieces? Um...no.

I guess it's normal if you develop a problem for something to be wrong. My alternator belt had a 1/4" slice in it...which is obviously either the cause of (or a product of) my problem in the first place. It was cut about half the total width of the belt, but it was only in one spot. Makes sense that it was squealing. The belt was slowly ripping and loosening itself.
Shredded!? though, I don't think it's normal for anything to be shredded. And I'd be pretty worried if my serpentine belt and my alternator belt were both shredded, lol. You must have a racoon living in your engine or something.

 

[flash75]

Salvrenz, this thread is on the Mazda 3 forum, his problems were similar to yours. Alternator cured his problems.

http://www.mazdas247.com/forum/showthread.php?t=123765091

Clifton