The 'E' Type Forum

Hi I am trying to wire a new loom to a new to me alternator . the alternator has one post for a ring terminal two large male spade connections next to it and a small spade connection the other side.
The wiring I have one thick brown and white with ring terminal a slightly thinner one and another thinner still .
I think the thinnest on is brown and purple .
There is no wire with a small spade to connect to the odd one.
Just stuck as I am not the best with this sort of wiring but I want to do it and understand it.

Hi
What model alternator is it? 10ac 11ac?
Have you checked out the wiring diags in the kb?

I cant see any model marks jus Lucas I will take it off to have a look. Thans

Model/part number is on the alternator under under the front pulley/fan....Steve

I will take off tomorrow.

Over 2 years to get a reply ....Steve

It seems that you have an early 4.2, and those did not use the 3AW. The 3AW uses the AL post on the alternator. Since yours may not have the 3AW, you would not use the AL post. Your ignition light on the dash is probably controlled by an oil pressure switch (not the same as the oil pressure gauge sending unit.)
Tom

Just to close off this topic and answer the question, I have recently replaced my original Lucas 11AC Alternator with an uprated 55 amp Lucas 11AC from SNG Barratt. I could have gone for their Self Regulating 70 amp Lucas 11AC unit, but I wanted to retain the original 4TR Alternator Control unit which is mounted under the heater fan unit. The Self Regulating unit does not require the 4TR unit, but requires minor wiring modifications.
I attach a couple of photos with the SNG Barratt guide photo showing the thick Battery connection where the Brown with White trace cable connects. It also shows the two Field connectors where the Brown with Green trace cable and the Brown with Purple trace cable connect. Of the two Field - and Field + terminals, the Field + terminal is the one inside a white plastic shield. Despite their names, they are not really sensitive to polarity, so you could plug them in either way and they would work. However, to be totally correct, by turning on the ignition to see which wire has 12 volt +, this wire goes into the shielded terminal. In my case the Brown with Purple trace is the Field +.
My 1967 4.2 car has the 3AW Warning Light Control mounted over on the chassis rail over on the other side under the carburettors which connects to the Ignition Warning light. In my case, this needs the smaller spade terminal connected to the 3AW using a White with Brown trace cable.
I trust this assists.
Regards,
Dave

The alternator will work with the field + and field - in either position. However, in theory, Lucas recommended the position of the wires as they did for a reason. Because of the geometry of the brushes on the slip rings, one brush travels further and faster than the other. Because the electrons travel in a particular direction due to + vs -, and that direction effects the brush wear, the proper wire positioning helps even out the wear.
Tom