The serpentine belt and alternator "are" related but does not mean both need replacement.
You were told your serpentine belt was going a week ago. How that is know is with inspection. Look at your serpentine belt has cracks or cuts or nicks etc. Usually the rubber gets old and starts to crack. I would say your belt has "visible" cracks . The cracks weaken the belt and it then starts to stretch. Usually when stretching starts the alternator is less capable of putting out it's full charge. Now add in your lights,radio,heater etc. The alternator is having one hell of a time trying to power up everything and not let the battery into the picture. Now the battery is not being charged by the alternator the way it should be. And then everything hits the fan and............... your battery is dead.
*1 The guy from AAA probably saw the belt was bad and stretched causing bad output of the alternator.
*2 The alternator is no longer functioning properly (Low or weak output) - 90% of the time the alternator is fine.
*3 To absolutely know if it "is" the belt do this:
Engine OFF - look at the belt going around you alternator pulley. About 3 - 4 inches away from the pulley push down on the belt with your finger. The belt should flex/move very little only about 3/4 inch full flex/movement. If the belt seems very spongy, soft and weak... a bad belt is starting to play a "BIG" roll in the problem. If you push down on the belt and there is a very large flex/movement like you are pushing on "clothes line rope"...you "should" find your alternator is "fine" and you just need a new serpentine belt.
If the belt looks good, has very little flex etc. I would start thinking the alternator just might be no good. - I am almost sure ...80% sure you will find the problem with a dead battery was caused by a bad belt.
The alternator needs the correct amount of tension applied to it so it will operate as it should.
I do not know what engine you have, I can just say on that ....a serpentine belt for a 5.0L 8 cyl. is around $50.00. You will also need to pay labor if you are not doing the work so.....Somewhere around $80- $85 for the belt and labor.
If it is the alternator... I do not know what your present amperage output is. The higher the output the higher the cost average price is $131 for the alternator plus labor for removal and installation.
You can check the price for the alternator out here at this link:
A good place and good prices.
Again, I would bet your just about say for sure you serpentine belt is the whole problem....around $80.00 or less ...(Belt & Labor).
** Tip, if you have a Advance Auto Parts near you they will check your alternator (Free of Charge)**
I hope that information helped. If you need any more help just send me a private message and I will get right back to you.
Wednesday, December 16th, 2009 AT 10:06 PM