8 replies to this topic

[minimadjack]

I have a 1996 SPi cooper 35 with a reaccuring battery charging fault, at first it was thought the alternator was the cause as the battery was only being charged at 11.34 volts (with lights, radio on etc). It was changed for a brand new unit and was assured by the garage the fault had gone away. I've since also changed the battery but the fault has come back. I don't know what else it could be as the two obvious componants have been replaced. Any help would be greatly appreciated!

[firstforward]

What is your actual fault? A flat battery or just the fact its showing 11.34 Volts? Sorry got to start somewhere.

[minimadjack]

The fact the alternator isn't charging the battery?

[minimadjack]

Anyone know if SPi alternators have an exciter??

[firstforward]

Does this answer your question....

 

http://www.theminifo...ttery-problems/

[minimadjack]

That link was very useful thankyou! I found that the small brown/yellow wire on the alternator had a loose connection on the female connector so I fixed that, readjusted the drive belt and I was getting 13.10 volts at the battery ( with no load). I then revved it to 4000 and the voltage fluctuated between 13.00 and 13.10 volts. With the engine still running I turned the lights on, it dropped to 12.50 volts and was gradually dropping. With lights on and revving ageing it only rose to 11.92 volts. I then turned as many things things on I could and the voltage dropped to 11.75 and fluctuated, I gave it some more revs and it still fluctuated at around 11.75 volts.
I've checked the other connections on the alternator and they're fine. The battery warning lamp comes on with ignition and goes straight out as soon as the engine fires up.
Does anyone think it could be the voltage stabiliser behind the dash as the above link says?

[xrocketengineer]

The warning lamp is working as it should so, it is unlikely that there is a problem with the instruments. I would remove and clean all the earth connections starting with the battery to body. Then I would add a second earth wire from the clutch cover to the body earth point by the body diagonal brace between the servo and the inner wing.

If that does not fix it, the positive battery cable could be suspect. But before replacing it, check with the engine running the voltage from an earth point to the alternator output and then at the connection to the starter coming from the alternator the brown/purple wires. If they have a poor or no connection, the car would start but the battery would no charge since basically the alternator output is disconnected from the battery.

[Trick77]

It sounds similar to a problem I created by changing the warning light for an LED as being a diode it prevents the current in one direction so that the rotor cannot be charged up. Just in case you have done anything similar

[xrocketengineer]

The more I think a bout it, the two brown/purple wires from the alternator might be the problem. They connect to the starter using a single fusible link and it might be fused.