# vintage lucas alternator conversion



## john carnie (Dec 25, 2018)

I have perkins 4.236 diesel engine 41 years old with siezed original alternator externally regulated which i hope to replace with internally regulated replacement.
Despite all the postings on the internet which describe some of the components I cannot find any detailing my situation. 
i need to identify the wiring attachements to the original and which to attach to the new.
i have attached pictures of the old alternator connection and the proposed new one which I would be grateful if anyone could give me some advice.





















I have no access to certified / trained mechanic to undertake the work due to my location in spain..
anyone can help?
regards
john carnie


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## RC Wells (Dec 26, 2008)

Here is a very straight forward instruction for a one wire alternator: https://itstillruns.com/wire-alternator-tractor-5009076.html

On your Perkins about the only concern is the direction of engine rotation is compatible with your alternator.

If you are using the $29 auto parts Delco alternator in the photo, which requires conversion of a three wire alternator to a single wire charging unit, this Youtube is what to follow:


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## Hacke (Feb 22, 2011)

Hi John

Welcome to the forum!

You seem to have a Lucas 11AC, which also is indicated by the name of the photo (11ac.jpg). Here is a wiring diagram:
http://the-norfolk-broads.co.uk/fileattachments/A/Alternator_charging_cct.jpg

You only need two of the old wires to make the alternator charge, they seem to be the one connected to F+ (which is the red one in your case) and the one connected to B+ (the light brown one at the red plastic marker).

You need the red wire for the battery charging warning light (this wire also excites the field at starts).
You need the light brown wire for charging the battery.

First, check that the wires are the correct ones:
Unhook all connections at the regulators.

Check the red wire:
Disconnect the red wire from alternator.
Turn the ignition switch to AUX ("ignition") position.
Connect the end of the red wire to good ground, the warning light should glow.
Connect the end of the red wire to battery (+), the warning light should go out.
If all went well, the red wire is the wire for the warning light.

Check the light brown wire:
Follow the wire from alternator, it should be connected to the starter solenoid battery (+) lug, or direct to the battery (+).


I cannot see any markings on the Anglo alternator, but the three spades should be either of type A or B in this presentation:
http://www.mgb-stuff.org.uk/altplug.htm

So, most likely, the red wire goes to the small uppermost spade (IND or WL) and the light brown wire goes to the middle spade (+).

If the terminals on the alternator are of type A, the bottom spade (B+) should have a separate wire connected to the battery (+). This is so the alternator can sense the actual voltage at the battery and regulate the charging according to that. If you have a wiring like the one in the diagram, you can use the wire that goes from the starter solenoid to C1 on the field relay and move the C1 end to the bottom (B+) spade.
However, it is common (but not correct) to connect the wires from + and B+ at the alternator, so the alternator senses the voltage there.

If the terminals on the alternator are of type B, the bottom spade does not need any connection to make the alternator work, but you can add an extra charging wire there. 

Normally, the alternator is grounded to battery (-) through it's body on to the engine and via a wire to battery, but it is good practice to run a separate wire from alternator body to battery. You can reuse the black wire for this.

It looks like a Lucas A127 clone. If so, one of the threaded studs is also for output to battery and is better suited for the light brown wire, but the other one should be a single phase output for a tachometer. It should also have type B terminals, so you only need to connect the red wire for the warning light at the spades.
To be safe about the terminals, contact the seller and ask for a wiring diagram.


When everything is working:
Buy a connector plug suited for the terminals:
https://www.polevolt.co.uk/acatalog/Lucas-Alternator-connector-with-terminals-ALTLCS.html#SID=53
https://www.tractorparts.co.uk/475-...ator-3-Pin-Wiring-Plug-Bosch-Universal-Fixing

Remove all the unnecessary wiring and components and replace the old remaining wiring with fresh wires and connectors.


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## john carnie (Dec 25, 2018)

RC Wells said:


> Here is a very straight forward instruction for a one wire alternator: https://itstillruns.com/wire-alternator-tractor-5009076.html
> 
> On your Perkins about the only concern is the direction of engine rotation is compatible with your alternator.
> 
> If you are using the $29 auto parts Delco alternator in the photo, which requires conversion of a three wire alternator to a single wire charging unit, this Youtube is what to follow:


thanks for pointing me towards a video explanation I can understand and for taking the time to reply at this time of the year
regards
john


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## john carnie (Dec 25, 2018)

Hacke said:


> Hi John
> 
> Welcome to the forum!
> 
> ...


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## john carnie (Dec 25, 2018)

hi Hacke,
thanks for the detailed reply posted and as with 
your reply has given me the necessary understanding to finally get on with the wiring.
I must have read about 20 different alternator guides but none of them are detailed in the step by step approach you have given.
i live in Ireland and my perkins is in Spain , I will be travelling there in 2 weeks when I will wire up the engine.
I will let you know how i get on.
As with RC above I really appreciate the help given particularly over this Christmas.

regards
john


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## john carnie (Dec 25, 2018)

Hacke said:


> Hi John
> 
> Welcome to the forum!
> 
> ...


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## john carnie (Dec 25, 2018)

Hello again,
further to your advice.
With the perkins circuit you supplied and the instruction to remove all the connections to the external regulators , i do not see how the "charge light" would extinguish when the alternator starts its charging counter current ,or am i misreading your guide?


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## john carnie (Dec 25, 2018)

Further reading answered my own query. The field wire is energised to the charging voltage and counters the battery voltage to extinguish the light.


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## Hacke (Feb 22, 2011)

john carnie said:


> ... The field wire is energised to the charging voltage and counters the battery voltage to extinguish the light.


Exactly, the alternator is at ground voltage at rest, and needs the external feed through the bulb to get magnetized at start. After start it produces it's own magnetizing current and reaches the operating voltage. Now it is the same voltage on both sides of the bulb = no current going through the bulb = light goes out.

If the alternator is faulty and not giving voltage above battery voltage when it runs, a current will flow through the bulb. That is the bulb's warning function. The same thing happens if the alternator reaches higher voltage than the battery, but the current goes the other way then.

The bulb's wattage is important, because it determines the current from battery through bulb and then through the alternator field winding at start. The magnetic field will not be high enough if the current is too low, and the alternator will not start charging. What I have found is that you probably need a bulb with 2-3 W, if your new alternator is a Lucas A127 clone. Higher wattage = higher current = better push. But again, ask the seller about it.

If the bulb is faulty you do not get any current at start, and the alternator will not charge. There is a way to save you from troubles. If you put a resistor in parallel with the bulb, you will have a current through the resistor even without the bulb. You need to calculate an optimal combination of bulb wattage and resistor resistance.


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