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alternator issues


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Have just fitted an alternator in place of a dynamo on my 196813/60 Herald. It is an older alternator, which I was told had been reconditioned and was due to be fitted to a Triumph Spitfire. It 's a 15acr with 2 x 3/8th spade terminals and 3 x 1/4 inch spade terminals. There is a thick wire coming out of one of the 3/8th terminals and, a thin wire , which I believe is the warning light, linked  to two of the 1/4 terminals, plus a wire coming out of the third 1/4 terminal [b+] don't know what this is. I have read that if you add another wire to the other 3/8 terminal and join it to the battery side of the solenoid, it improves the alternator output. I have also joined up all the appropriate wires which were attached to the regulator box. However, when I went to connect the battery, BIG sparks!  I disconnected the extra cable from the alternator to the solenoid, and it was ok when I connected up the battery. Can anyone tell me what I had done wrong and is it likely that I might have damaged the alternator?  Thanks!  Webbo


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Hello Webbo.


Oooppps !!!


Firstly may I suggest having a look at Darren's website: www.www.triumphherald1360.co.uk


It is very interesting and has an electrical subsection which includes alternators - this will certainly start you in the right direction. Additionally, there are numerous articles on the web that cover this job.


Personally, I would not bother with older "known to be good alternators" as you cannot tell what their true history is.


New alternators are cheap enough on the net and come with a guarantee.


With regard to damage - difficult to know; it certainly will not have liked the sparks and they are quite delicate to wrong way voltage etc.


Strip everything out and start from basics.


I'm sure either PL or Darren will pick this up and assist you from there; plus other knowledgeable forum users.


I do not think it's all bad news, not just the best start.


Good luck.



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in basic terms at the regulator join all 30amp lucar wired together 

join the 17amp lucar blades together  but not the earth  ...its not needed 


connect the orig 30 amp  lucar to any one of the two on the alternator ( as both are the same )


join the orig 17 amp to the WL terminal  on most lucas the two are again the same


some require an additional  battery voltage sensing wire .    B+  not really needed   this unit may be from vauxhall who did use the extra feed 

to best of the grey matter  triumphs ,rootes , BL  etc   never have this option.


its best to run a new heavy gauge wire direct from the alt  30amp  to the solenoid battery eyelet  and remove the old harness



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Double check your wiring where the control box used to be:


1. The thin black earth cable is not needed and can be disregarded.

2. The thin Brown/Green & thin Brown/Yellow cable should be joined, this is the connection between the small field terminal on the Alternator and the dash warning light.

3. This should leave you with 5 thicker cables, 2 x Brown/Blue (Lights), 1 x Brown/Yellow (Alternator) & 2 x Brown (Solenoid & Horn), these need joining together.


Every Lucas ACR Alternator I've ever worked with has only has 3 terminals on the back, the 2 larger ones (3/8") which feed back to the battery, and one smaller (1/4") which goes back to the warning light on the dash. You should be able to use a standard Lucas connector like this one:




The additional wire is to do with the output of the alternator. The standard wire on a Herald loom will only be good for 25amp, so if the alternator has a greater output then use the second large terminal to run another cable back to the battery.


To test the Alternator you could start the car without the alternator connected and connect a multi-meter to each of the terminals, if you get a reading of 12v or more then you know it's charging.


Hope that helps.

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Many thanks for your input gents, I have discarded the earth at the control box and will check again the rest of the wiring there. At the moment it seems ok but am not able to start the car to check to see if it works . However I am still confused that when I ran a cable from the second terminal on the alternator to the battery side of the solenoid it created massive sparks when I tried to connect up the battery. So it seems that I will not be able to run an additional cable, but seeing that the alternator is only 15acr I think the 25amp cable capacity will be ok, I hope . Webbo

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Are you sure it’s the alternator that is causing the sparks when you attach the battery terminal, and not something else shorting or left on?

However as thescrapman says five terminals points to an odd style of alternator that may not use the same wiring as tyne more common versions fitted to Triumphs. I’d look for a three-terminal version and fit that, just to be sure.

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