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Wiring Check. Alternator wiring.

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cjowett

Freshman Member
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72MGB rebuilt Alternator but no wiring reference.
Can anyone tell me where the Black, Brown and Yellow wires connect to?
It may need someone to go and look at their own just to check but I would be very grateful as I have been trying to find out for over a week now.
Thanks.
 

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What's the part number of the alternator? There are different alternators, and the rectifier wiring is specific to the alternator being used.
Jeff
 
There should be no black wires going to the alternator. The solid brown wires go to the larger terminals with the larger gauge wire going to the middle terminal. If there is an 'exciter' wire it goes beside the big brown wire on the large terminal adjacent to it. The small brown/yellow goes to the small terminal. This is assuming you have the three terminal alternator. Check/clean the connections on the starter solenoid . Also , make sure the alternator light works correctly.

Alan T
 
Alan, he is referring to the internal wiring of the regulator, judging by his attached picture. Just need to know which alternator.
Jeff
 
Oops.....missed the pic. The original alternator had a three or four wire regulator. Rebuilders typically replaced it with a two wire and connected it differently. So is that regulator a two wire regulator?

Alan T
 
Well I have a perfect image of the alternator you need to see but cannot get it to download because the file is too large. Anywho , the black wire goes under the brush holder bolt (ground) , the yellow wire on the outer brush contact and the orange wire opposite the yellow on the same contact.
There should be a jumper connection from the center brush to the top of the regulator .
Alan T
 
I'm afraid it has no part number visible. I'm going to see if I can work it out by the post that AlanT has written. Thanks for your help.
Colin.
 
OK, that is well described and should help me get my car on the road. I'll let you know!
Thanks
Colin. /ubbthreads/images/graemlins/driving.gif
 
It Runs!!!!!!!

Ignition light is still on but I think that is because the battery is so old and needs replacing.
 
Ignition light only comes on when the alternator is not working right... It's not a battery light.... Unfortunately. /ubbthreads/images/graemlins/frown.gif
 
Before condemning the battery, charge it for a good while and try again... worth a shot.
 
Worth trying. I like to save money. I come from Yorkshire in the UK where we keep our wallets under lock and key! /ubbthreads/images/graemlins/england.gif
 
My wallet hasn't been seen nor heard from since 1995. /ubbthreads/images/graemlins/grin.gif
 
AlanT,

As my Ignition light is still on I suspect I did not fully understand your response but if you have an image would you mind sending it to me by e mail?
My address is colinjowett@gmail.com if you wouldn't mind.
Thanks,

Colin.
 
Colin,
The image has been sent to you. The extra piece with the yellow wire is a surge diode and not found in too many rebuilt units.

Alan T
 
Well, I made the change and it runs perfectly with no ignition light on and the battery seems to be holding charge again. Thanks for your help, it's great knowing that there are others willing to help.
/ubbthreads/images/graemlins/cheers.gif
 
Colin,
Make sure the light comes on with the engine off and the ignition on. Then if it goes out when the engine is running it almost has to be charging.
Alan T
 
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