Red battery light on.Help!
 

well, good thing i was close to home when I noticed the red battery light on...

turned around to hook it up to DIS and it gave me a bunch of odd errors like

-relay, heated rear window-faulty
-steering wheel column radial - transmission fault
-electronic braking-force distribution fault
-brake light, right, faulty

the car doesnt start anymore...

I know a low battery throws a bunch of electrical errors but the battery is one year old.

I'm thinking alternator? How can i be sure?
I read that an instantaneous red battery light is often an indicative of a broken accessory belt.

Haven't checked that yet...but i suppose you lose power steering, alternator ofcourse and water pump that leads to overheating...well i had power steering, didnt drive enough to overheat, etc

Ordering an alternator will take a while, ill be stuck in the house this weekend...not fun at all.

How hard is it to replace the alternator on a 4.8?I've only done it on my E39 530i and that was pretty simple.

If it turns out to be the alternator, other than replacing belts, what else can I do "while in there"?

thanks guys i really do appreciate all the help i can get.

Well I can't speak for the 4.8is but when my X threw the battery light it ended up being the alt. Checked the voltage with a muti-meter with the car running and everything seemed to be ok but only when in drive and running some accessories didn't the voltage drop to 11v. So must likely it's going to be the alt. All of those error codes are most likely caused by insufficient voltage.

if your battery is dead after a year then its probably the alternator. if you remove it bring it to most auto part stores and they can test it's output.

Be aware the auto parts store only does a "cold check".

I've had 2 alternators that checked ok cold, and would regulator fail when heated to under hood summer operating temps. Not the E53 alternator.

True. Charge your battery to keep form killing it. some don't come back to well if they sit too low for too long.

Ordering an alternator takes a while?! You can walk to the auto parts store on the corner and get one off the shelf. If the shelf is empty, they can have one the next day if you discover the shelf is empty early enough.

And,the battery light does not point to the battery because the light is really a Charging System Light. A picture of a battery is easier to understand than a picture of an alternator, which is the typical problem when the light comes on.

Guys, thanks a lot so far.Id like to avoid auto parts store for the very reason of inconsistency in their product quality.Bought a reman.unit for my E39, installed it, only to find out the pulley makes an awful sound...take it off, bring it back, get another, you can understand the frustration...
Rather go OE this time...

Could be the regulator. That was my fix. You can also take yours to be rebuilt. The job is fairly easy. Removal is also easy. Take out fan. Intake. Disconnect battery. Make sure you disconnect battery. Remove 3 bolts. Maybe remove pulley. I forget. But very straight forward job.

Hey Slick thx but if it is the regulator,might as well get a new alternator right?how much does it cost to rebuild them?
Does 550$ sound steep for the genuine BMW alternator from ECS?

^Not necessarily, if its just voltage regulator the rest of the alt should be good.

$550 for genuine is steep, especially since the VReg is about $110 IIRC

Personally I'd probably test my known good alternator and rebuild it before replacing it at 5x the cost. Sort of like re-boot your good OE axles before they bust open, at $20 per side instead of a new GKN axle at $280 per side

The regulator is like 15 bux. Do some googling how to rebuild your part number alternator. They are all basically the same. Do some Emory cloth cleaning on the copper spool thing. Took about 1.5 hours total on me. If the copper spool thing is gouged though, bring it to a rebuilder and wait 30 min for them to do it. Easy.

Oh and maybe search for my post here on alternator rebuild, I must have some notes there.

This might help or not.

My truck was starting fine after the Red Battery light episode, but I am a freak of always connecting all my vehicles to a trickle charger almost every day.

With the truck started, I heard weird noise using stethoscope ( it was the Bearings). If it was the voltage regulator , I would have elected to replace the part.

So Double check the alternator bearings ( and diodes as well).

I paid ~400 for a genuine alternator for 3.0 and kept the old just for home experiments

Good luck !

Awesome guys , thanks for the advice , I will get on it and see what I can come up with.
When this happened to me yesterday, I had a dark thought to go ahead fix it, trade it in, get a 08-09 cayenne gts
But then, I looked back at it while entering the house and I'm like, nope, this baby ain't going anywhere.fix it and keep it.:)

I like the Cayenne GTS, just not how I have to look twice to see if it's a Porsche or a VW with big wheels/tires. :rofl:

That must piss the GTS owners off.

I would charge the battery, check voltage with multimeter or from the cluster, leave the charger connected and start it up, disconnect the charger and either read the cluster for alternator output or read with multimeter connected to the battery---most likely bad alternator but I always like to make sure before I buy something, install it and problem is still there.

So, buy new not rebuilt.

Changed the battery with a fully charged one.
Unlocked the OBC, test 9 and got 11.4 V
Turned on the AC, and it went to 10.9v-11.0v
So I guess I need to rebuild the alternator.

You need an alternator or the voltage regulator. The new (rebuilt or new) alternator comes with the regulator, or you can replace the regulator by itself.

Somebody said that the regulator is 15 dollars. That's not entirely true, indeed it is mostly false, but the regulator is far less than the entire alternator.

The regulator collects the AC electricity that is generated, and converts it to DC that the car can use. The conversion is done with a circuit called a bridge rectifier that is built out of a series of 4 diodes. One or more of the diodes can fail, and the rectifier circuit breaks down. The regulator also uses a pair of brushes that ride on the commutator (shaft) of the alternator, and the brushes can wear out.

When you have the alternator out, the place where the various wires attach is the regulator, and two more screws will have it out.

Yea I said $15, just because I forgot. But this is it at auto warehouse.
BMW X5 Voltage Regulator - Free Shipping - Bosch, OES Genuine

That being said. Get the oe BMW one even cheaper through Craig at Openroad BMW. It is a fraction of the cost of an alternator.

Unless the engine is running, you know nothing about the status of the alternator.

Start the engine and measure the voltage, you should see something in the range of 14.5v, give or take a few tenths.

Alternator is not rebuildable, gotta get a new one...
In the process of removing it, the brittle nipple on the plastic connector where the small hose connects the upper rad hose and expansion tank broke off, not sure if I should glue it back on until I tackle the whole cooling system?

Power steering hoses leak like crazy...oh well...one job at a time.