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Alternator Only Works Some Times


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#1 Dandelion

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Posted 08 October 2015 - 09:38 PM

Hi new alternator 4 months ago when bought car as not working ,fine over summer but issue now wet and dark. Have tried another new alternator and new battery, checked for cable problems and cleaned earths.

 

 

Issue- start 1990 mini with 65amp alternator, whilst on choke with revs up off tick over getting 14.2 volts to battery.

 

Turn on headlights, turn on heater blower and rear screen still getting 14 volts at battery.

 

When choke off revs at tick over voltage at battery down to 12.5 volts with battery normally ay 12.7 before starting.  I believe alternator only gives 14 volts at 2000 rpm?   Issue is increase revs and voltage does not rise again.  As if alternator not cutting back in to charge with revs.  

 

Belt is tight, battery light on when turn key before starting, then goes off and does not come back on.  Question is it a bad cable or alternator.

 

Have tried alternator 4 months old and replacement new one and both do same so i presume issue on car.  

 

Have tried running with no load, i.e. start car, turn off choke to idle with no load and at tick over battery still getting 14.2 volts

 

 

Thoughts please thank you. My 2 thoughts either wire issue under load or alternator.  

 



#2 KernowCooper

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Posted 08 October 2015 - 10:45 PM

I would be checking the terminals connected to the alternator to ensure they are clean and check and the connections to the cables where they connect to the starter solenoid
If you take the revs up higher than 2000rpm does it start to charge then?

Edited by KernowCooper, 08 October 2015 - 10:46 PM.


#3 Dusky

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Posted 09 October 2015 - 07:40 AM

I had the same problem, also swapped the alternator. In the end it was the starter solenoid + nut comming loose.

#4 adam_93rio

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Posted 09 October 2015 - 09:24 AM

As said, check the positive terminal on the starter. I've had them actually come loose in the end of the starter before. So the entire stud moves, this caused a charging issue




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