donberry
12-24-2004, 08:04 PM
1992 525i, battery not charging. I first checked battery light etc, all was well. Bought a new alternator, still no charge. Going thru Bentley's, it says to check for voltage on alternator at the main cable to battery and the d+ post on alt.
On main to battery, no problem, 12 volts....
with key on , only about 1.4 volts.....hmmmm, seemed like I found my problem.
Troubleshooting the wires, I found that if I disconnected the blue wire from the alternator, I then had 12 volts.......so problem must be in NEW alternator- right?
well, started checking out alternator. The way it is made, the brushes themselves on one side is actually grounded to the case. So whenever the alternator is bolted on, it is grounded, which is why I only get the low voltage.
It does not make sense to me why the book says to check for voltage. Though it does not say how much voltage. I checked the old alternator and another one and they all were grounded thru the blue wire (D+ post).
Hope this makes sense.
Anyway, are their any expert mechanics....
I have 12 volts everywhere I am supposed to, except the blue wire as it is grounded....
symptom is no charge....
The only thing I have not done yet is replace the unloader relay which I am working on getting one now.
Any help would be greatly appreciated.
On main to battery, no problem, 12 volts....
with key on , only about 1.4 volts.....hmmmm, seemed like I found my problem.
Troubleshooting the wires, I found that if I disconnected the blue wire from the alternator, I then had 12 volts.......so problem must be in NEW alternator- right?
well, started checking out alternator. The way it is made, the brushes themselves on one side is actually grounded to the case. So whenever the alternator is bolted on, it is grounded, which is why I only get the low voltage.
It does not make sense to me why the book says to check for voltage. Though it does not say how much voltage. I checked the old alternator and another one and they all were grounded thru the blue wire (D+ post).
Hope this makes sense.
Anyway, are their any expert mechanics....
I have 12 volts everywhere I am supposed to, except the blue wire as it is grounded....
symptom is no charge....
The only thing I have not done yet is replace the unloader relay which I am working on getting one now.
Any help would be greatly appreciated.