Alternator / battery light!!!!!!

Hey guys, Ive got my battery light coming on and off. My battery is too weak to start my car but my car has never died while driving. Drove over 75 miles 2 days ago and it didn't die while driving. I can get a jump off of a buddy and it starts IMMEDIETY after hooking up. When I try to start the car it just clicks...

All of this started on Christmas when it snowed like 2 feet. And the temps have been in the teens to high twentys almost everyday since.

So what I need to know: is my alternator or voltage regulater going out?
: is it the cold weather?
: is my starter going out ?
Thx !

Use cluster test to see if it's battery, alt, or both. The alt isn't a charger, so if you've had a bad battery for a while, the alt could go bad.

Voltage off should be around 12 V and on around 14V.

Your starter isn't an issue at all.

I'm thinking just battery, but you need to check the voltage to begin.

Search Cluster test.

Ok so when you say cluster test , you mean what exactly?

Sorry I don't know all the lingo and their meanings yet

Scratch that last post

Replace your battery.

Just did that today actually...

Ok so what am I looking for exactly... How do I "read" this?

No, the hidden OBC menu, not the bulb test. Search, covered 10000000 times.

Battery probably fixed it.

So was this what I was supposed to do???
If it was the alternator, what would indicate its failure?

Find solidjake's vid of cluster test...voltage is #9...you can see voltage of car off and on...and you should still do this...or if you have multimeter, just use that and report voltage you have.

If you have new bat, but alt is bad, you'll run into this issue again.

But, hope you just needed battery...although, it could have just been how you were using your battery too...too many short trips, not enough long ones.

You're gonna most likely need a new alternator and maybe battery as well. It sounds like the alternator is still working to some extent, but not charging enough to keep the battery up to charge. If the light is on, it means the alternator is bad.

Good way to check is to run a voltmeter across the battery while the car is running. Running and charging should be between ~13.5-14v, fully charged battery with the car off should read about 12v. If it's making <13v with the car on, alternator is bad.

Ok so bad news of course , got a reading of just 12.35V.
I've been lookin for a replacement but I'm very confused... ECS has them at 120A, but autozone and oreillys has them at 89A and 140A.
Now I imagine the 89 will not do, but will 140A be too much?

You need to find out which one you had to begin with. I believe the Bosch alternators were the 120A and the Valeo were the 90A alternators.

Just recently for the m3 I was able to get a Bosch alternator for $200 with my core deposit

Mine is 120. I had to remove it a month and half go to replace my oil filter housing gasket.
Wow, where did u score that deal?

Originally Posted by Wormydog

Mine is 120. I had to remove it a month and half go to replace my oil filter housing gasket.
Wow, where did u score that deal?

One of my mechanics get's amazing deals on parts, and he just hooks me up with parts at cost, even if I'm doing the work myself. He's pretty much the man

I'm pretty sure he got it right from the Bosch HQ in NJ near us.

UPDATE!
So while waiting in traffic today, my battery light came on and stayed on for maybe a minute...
Then went off and hasn't come on for over 20 miles now. Could I maybe have a loose cable?
I did remove the alternator a month and half ago when replacing the oil filter housing gasket. Also, after a week and a half of nt starting without being jumped, it has started up 4 seperate times today

Something is loose...tighten things up...learn to use the cluster test to keep an eye on things...but this sounds like a loose/corroded connection...and I hope you get lucky and that's all it is.

Start at battery...alt...+ terminal...grounds

GL

Originally Posted by dmax

Something is loose...tighten things up...learn to use the cluster test to keep an eye on things...but this sounds like a loose/corroded connection...and I hope you get lucky and that's all it is.

Start at battery...alt...+ terminal...grounds

GL

+1, definitely could be something loose, check the obvious things first!

How do I use the cluster test exactly?!?
Is post #7 not the cluster test?

That is the cluster test, but you want the hidden OBC menu:

http://www.pistonheads.co.uk/gassing...p?h=0&t=483538