Good evening
I have a 1995 Mini Cooper Si (an SPI model).
My alternator stopping charging the battery a couple of weeks ago, and after reading every relevant thread on TMF I can find and testing things, I need to post to ask!
The battery seems good - it charges to ~12.5 V off an external charger, and runs the car for a couple of hours before dropping down to ~11 V. If the car isn't used, the battery holds its charge well - certainly more than a couple of days, but I haven't left it any longer to test.
With the ignition off, I get voltages as follows:
At alternator small exciter wire lucar connector: 0 V
At both alternator large positive lucar connectors: ~12.5 V
At solenoid end of positive wires to alternator: ~12.5 V
Battery indicator light is off as expected.
With the ignition on but engine off, I get voltages as follows:
At alternator small exciter wire lucar connector: ~1.5 V
At both alternator large positive lucar connectors: ~12.5 V
At solenoid end of positive wires to alternator: ~12.5 V
Battery indicator light is on as expected.
With the ignition on and the engine running, I get voltages as follows:
At alternator small exciter wire lucar connector: ~14 V
At both alternator large positive lucar connectors: ~12.3 V
At solenoid end of positive wires to alternator: ~12.3 V
Battery indicator light goes off again as expected.
With my multimeter set to resistance mode, I get a current between the alternator body and the car body (earth) even with the alternator connectors disconnected, which I think means the alternator is earthed well. Is this right?
As you can see, the battery light is behaving normally, and the small alternator terminal is reading ~14 V with the engine running which I *think* means the alternator is working. Is this right?
I hope the format above is useful, it's all the light/voltage information that was ultimately posted in other threads. WIth all that in mind, does anybody have any idea why I'm not seeing alternator voltage at the positive terminal?
Of note: The positive terminals on the alternator look quite rusty, but the exciter terminal is quite clean. Might it be as simple as rusty connectors? I have been assuming not, as the connectors are quite large and the voltage should reasonably high which I think will deal with a rusty connector. I have tried to clean off the rust using a solution, a small wire brush, and sand paper, but couldn't shift any of it.
I have attached a photograph of the terminals so you can see their condition.
Thanks very much
Luke
Edit:
Apologies for any incorrect terminology, I've learnt most of what I now know about alternators in the last couple of weeks!
Attached Files
Edited by l_bratch, 03 September 2015 - 09:57 PM.