8 replies to this topic

[robminibcy]

Hi all.

 

My mini has decided that as its Christmas she deserves another present!

 

Its a 79 mini 1000 so has the solenoid on the inner wing.

 

I have no batt warning light and as a result no charge going to the battery. The battery is pretty much brand new Bosch 075 and voltage is 12.5 v. The car starts fine and all other electrics work fine.

 

I went out to investigate the problem today and the batt warning light did come on once when I turned the ignition on but not since I have checked connections at the alternator, the solenoid, the battery and the warning light. The bulb works fine so am a bit stuck now!

 

I have voltage at the big brown wires going to the alternator which suggests to me that there is a problem somewhere in the warning light circuit as power is not getting from the battery to the warning light or getting a complete circuit.

 

Are there any standard tests I can do to try and narrow down where the problem may be or is my logic wrong and the problem is likely to be else where?!

 

Also my plans were to fit an uprated alternator. I have uprated wires ready to fit. Do the large brown ones I need to replace run from the alternator with one on the stud on the solenoid and one to the large spade connector on the solenoid? Id rather get the existing problem sorted before I start throwing money at it to upgrade and find it still doesn't work!

 

Thanks and Merry Christmas!

[robminibcy]

I have just tested the warning light for voltage and got 12v from the white wire. 0 from the brown and yellow. Is this correct. I so would I be right in thinking that there is a fault somewhere between the warning lamp and the small connector on the alternator?

[robminibcy]

further development!

Tested for continuity between brown and yellow wire at the light holder and the small connector on the alternator and that's fine so looks like alternator has had it.

 

put another alternator on and ignition light has returned!!! the second alternator I tried was actually replaced with the broken as it was behaving strangely and occasionally the ignition warning light wasn't working or lit dimly. can/ do alternators fail intermittently as would seem to be the case here?

 

either way it seems a new alternator is on the cards (the credit card that is!).

 

so to conform the wires I would need to upgrade to fit a 70 amp alternator are the two brown wires with the big connectors on the alternator. Does one go to the stud on the solenoid and the other the large spade terminal on the solenoid?

Edited by robminibcy, 27 December 2014 - 06:36 PM.

[KernowCooper]

Quick test for the warning light is remove the warning light wire from the Alternator and touch it to earth if the light comes on its the Diode pack at fault.

[robminibcy]

Quick test for the warning light is remove the warning light wire from the Alternator and touch it to earth if the light comes on its the Diode pack at fault.

yep, light works fine like this. alternator diode pack confirmed as broken. thanks

[Spider]

It is most likely as KernowCooper has suggested (Rectifer Pak karput), however just check that all the +ve connections (Thick Brown Wire) back to the solenoid are good first and that with the engine running, the Alternator is spinning (eg, could be a siezed water pump).

[robminibcy]

yep certainly the alternator diode, the alternator spins fine and all other wiring is intact.

[dklawson]

Yet to be answered is your question about whether alternators can work intermittently.  My answer is "sometimes yes".  In particular, if an alternator has many hours of service and the brushes are at the wear limit they may work for a while and then drop out.  The next time you start the car, the alternator may work again for a short while and again, drop out.  Replacing the brushes can address this if the slip rings are not badly worn or damaged.  Other things that can produce intermittent operation are cold/bad solder joints in the alternator.  

[robminibcy]

I think 36 years would count as many hours of service!! There is a bit of play in the shaft as well so ill treat it to a new one.