BimmerFest BMW Forum banner

2000 Z3, 2.5, alternator questions

2K views 6 replies 5 participants last post by  cdaubs 
#1 ·
So my wife drives the Z3 and she tells me that in the morning the battery idiot light stays lit for a few minuutes after she starts and drives the car. I inspected the battery and discovered that the secondary positive battery cable (to the airbag control module??) was very warm to the touch and had seemingly melted a hole in the red plastic cover over the positive battery terminal.

Not having a BMW dealership in our town I took it to a local speciality shop for advice. They told me the damage to the positive feed cable was due to corrosion causing resistance and heat, they also put a test meter on the battery and said that the alternator is taking an unusual amount of time to kick in and start charging the system (30 seconds +/-). Additionally they said it is putting out too much voltage (14.25 volts).

The car has a 2.5 engine and currently has a 90amp alternator. To replace the alternator and repair the damaged wire is going to cost $475! YIKES :cry:

So, I am looking for advice on:

1. Where to get an alternator - They were quoting $305
2. Is it difficult to replace my self - I have lots of tools and a good working knowledge of how to use them
3. Any other info anybody can offer

Thank you all in advance :thumbup:

Charlie
 

Attachments

See less See more
3
#2 ·
Pop out the alternator and take in into a local store that tests those units. If the unit puts out the proper voltage on the stand you need to look elsewhere for the problem. When an alternator goes replacement brushes are cheap and a replacement voltage regulator is not too expensive; if you can locate such parts.

Richard
 
#5 ·
Make sure you remove the negative terminal from the battery first. That way if you should happen to make contact with the frame while removing the positive terminal you won't damage the alternator.

I am leery of the shop's diagnosis of your alternator. My car did the exact same thing and my problem was that the connection for that particular cable was slightly loose on the terminal.

I still haven't replaced my cable but I did clean the connection and made sure that it was good and tight. My charging problem hasn't returned.

Battery voltage should measure around 13.2V (1.2V x 6 cells) and most voltage regulators are designed for a charging voltage of around 14.4-14.5 volts.
 
#6 ·
All the above advise is great..I would take the alt out and take it to a auto parts house they will check it out for free..I would also check the drive belt, if that hasn't been replaced for awhile, if the belt slip then it won't charge right. G/L

To take the alt out is easy..just make sure you disconnected the battery before you do it, other wise you will short something else out..Two bolt and the drice belt if I remember right...It is not that hard to do..
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top