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Home > General Chat > Alternator voltage....

garethlloyd

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270 Posts
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Birmingham

HI guys,

I feel like this is a really stupid question but I could do with some help please.

I've just bought an old mini and it has been fitted with a lightweight denso alternator which I suspect is not charging the battery as everytime I come to drive it the battery is dead (even straight after a long run)

I've charged the battery overnight and it seems to hold charge ok. I've tested the alternator with a multimeter and it was kicking out 12 volts. Am I right in thinking it needs to be kicking out at least 13.8 to charge the battery?

The alternator is a Denso 16404-64012 which seems to be from a Kubota tractor or something. What is confusing me is that the alternator is stamped 12v. Does this mean that it is only supposed to kick out 12v and its not actually broken but not up to the job or is this something else?

If it is 12 volts can I just fit a different voltage regulator to get it up to the right voltage or is it no good?

Thanks,

Gareth


Tom Fenton
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Fearless Tom Fenton, Avon Park 2007 & 2008 class D winner

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Rotherham South Yorkshire

Check voltage engine off. Start engine. Voltage should then increase. If it doesn't, alternator isn't doing anything.
Even though it's stamped 12v I'd expect it to kick out 13.5v give or take. The 12v stamp I would suggest is to distinguish it from a 24v alternator as will be used on larger bits of kit.


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sim_ou_nao

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Porto/Portugal

I had the same problem, it was a wrong connection on the alternator...

Pedro Silva

http://miniciados.blogspot.pt/


Joe C

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Carlos Fandango

Burnham-on-Crouch, Essex

yep it should be kicking out more than 12v, sounds like its not wired up right or the reg has died.

i have killed a reg before, but fortunatly they are pretty cheap

http://www.ebay.co.uk/sch/i.html?_from=R40...0001800&_sop=15

On 28th Aug, 2011 Kean said:
At the risk of being sigged...

Joe, do you have a photo of your tool?



http://www.turbominis.co.uk/forums/index.p...9064&lastpost=1

http://s95.photobucket.com/albums/l154/min...2006/?start=all



Joe C

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Carlos Fandango

Burnham-on-Crouch, Essex

some good info here...

http://www.turbominis.co.uk/forums/index.p...t&tid=2995&fr=0

On 28th Aug, 2011 Kean said:
At the risk of being sigged...

Joe, do you have a photo of your tool?



http://www.turbominis.co.uk/forums/index.p...9064&lastpost=1

http://s95.photobucket.com/albums/l154/min...2006/?start=all



garethlloyd

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270 Posts
Member #: 616
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Birmingham

Thanks guys,

I've not retested it with the multimeter yet but looking at the diagrams (and thanks for posting the links) it doesnt look wired up correctly anyway!

Am I right in thinking the terminal with the rubber gromit bit with the tread on should be wired into the starter solenoid

Again, apologies for the stupid questions but seeing those diagrams have made me think its not wired correctly anyway!



Joe C

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Carlos Fandango

Burnham-on-Crouch, Essex

yep you need to connect the bolt to battery live, normaly via the solenoid.

also more info on the wiring below, you need the switched live to activate it the charging circuit, the other one can go to the lamp, and just ignore the sense.

On 28th Aug, 2011 Kean said:
At the risk of being sigged...

Joe, do you have a photo of your tool?



http://www.turbominis.co.uk/forums/index.p...9064&lastpost=1

http://s95.photobucket.com/albums/l154/min...2006/?start=all



garethlloyd

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270 Posts
Member #: 616
Senior Member

Birmingham

Joe C, thank you very much for all your help and thank you to everyone else that replied too.

I feel like a bit of a tit but wiring and aftermarket alternators are not my strong point.

Just got the multimeter on the threaded post and it seems to be kicking out a good voltage.

My plan is (unless someone tells me its not correct) to get one of these and wire it from the post to the live post on the starter solenoid.

http://www.halfords.com/workshop-tools/gar...ry-cable-22cm-9




What I don't understand is how someone has fitted it and not wired up the most important terminal on it!




Edited by garethlloyd on 14th Apr, 2017.


garethlloyd

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270 Posts
Member #: 616
Senior Member

Birmingham

For ref this is quite a good picture too


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Joe C

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Member #: 565
Carlos Fandango

Burnham-on-Crouch, Essex

that halfords strap looks a bit over kill, not that theres anything wrong with that,

basically the alt will only ever provide 40ish amps, so you dont really need massive wire, also the alt terminal is M6 so you'll need a washer either side of that strap to clamp down on it.

On 28th Aug, 2011 Kean said:
At the risk of being sigged...

Joe, do you have a photo of your tool?



http://www.turbominis.co.uk/forums/index.p...9064&lastpost=1

http://s95.photobucket.com/albums/l154/min...2006/?start=all



garethlloyd

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270 Posts
Member #: 616
Senior Member

Birmingham

Thanks again, what size cable would you use? Cheers


Joe C

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Member #: 565
Carlos Fandango

Burnham-on-Crouch, Essex

Somthing like this doubled up, that's pretty much what was in the original looms,

http://www.ebay.co.uk/itm/like/15247771765...3D1200686241926

On 28th Aug, 2011 Kean said:
At the risk of being sigged...

Joe, do you have a photo of your tool?



http://www.turbominis.co.uk/forums/index.p...9064&lastpost=1

http://s95.photobucket.com/albums/l154/min...2006/?start=all


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