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MG Midget and Sprite Technical - alternator conversion

I am replacing my dynamo with a 45amp with a 45 amp alternator and removing my regulator. I have trawled the archives and come up with lots of conflicting and confusing information.
Can anyone give me the definitive answer?
My regulator is marked -
E (Thin Black)
D (Brown/Yellow)
WL (Thin Brown/Yellow)
F (Brown/Green)
B (Two wires both Brown)
I don't want to connect it wrong and melt my loom!

Dave Brown

Do I just connect the D and WL (both Brown Yellows) together and then connect the B and F (two Browns and a Brown Green together?
Dave Brown

Dave, which alternator are you using and what loom connections does it have?

It's actually easier to leave the regulator in as a "terminal block" but if you want to remove it;
Here goes:-

E - Black is an earth for the regulator and can be connected to any convenient point on the body or removed altogether if it doesn't go in to the loom.
D - Large Brown/yellow goes to the large terminal on the alternator and should be connected to the Brown wires on B
WL - small brown/yellow goes to the warning lamp on the dash and should be connected to the small terminal on the alternator (assuming you have a traditional Lucas model)
F - Brown/green is spare but can be used to connect the small brown/yellow if you don't want to run a new wire of the correct colour to the alternator.
B - Two brown wires are the standard 12v supply to/from the battery and fuse box. As above, these need to be connected to the alternators high current output (large terminal) via the large brown/yellow cable. To be ultra safe I would run a second wire to the alternator especially if you intend to add extra load in the form of additional accessories eg fog's, spots, ICE!?

M McAndrew

Dave check out PaulH site at

loads of good info on how to convert.

M McAndrew

Im a big fan of a single wire alt...there just so easy...and have built in regulators
Prop and the Blackhole Midget

What car do you have Dave and what voltage regulator do you have?

I will send you a sheet explaining exactly what you need to do to convert.

But to do that correctly you must specify year model and type of reg.

There are 2 types of regulator, 2 and 3 bobbin, the later being fitted only to later MK111 midgets and MK4 Sprites?
Robert (Bob) Midget Turbo

I did mine from info on the net. I cant remember the link, but im sure youll come across the info you need fairly easily.
I used a terminal block instead of keeping the regulator

S G Macfarlane

I have a 1275 1972 midget (it may be a 71, I can't remember, it is L reg).
I have connected the two small wires (brown yellow and brown green) together and the three thick wires together. It seems to work ok. The warning light light comes on when the ignition is on, goes off half a second after the engine starts and I got 14.4 volts at the battery at idle (900 rpm).
Dave Brown

Dave - 71 and 72 are the same, so don't worry!

That's pretty normal, and a good voltage from the battery.

If you want to do the alternator conversion, then, the best and simplest website to use is actually the one from MGA Guru (, he describes things logically and in a way that takes you through step by step - with full diagrams.

Others have tried to emulate him, and, whilst I haven't checked out the above sites, I would certainly recommend this site to be bookmarked and refered to in the first instance in all matters.

Hi Dave sadly there is a big difference between the 71 and the 72 one has an early voltage regulator on it whilst the other has the later and unusual 3 bobbin regulator on it.

You need to confirm which you have.
The problem is that as different models came and went then wire colours changed.

Firstly what regulator do you have and when you removed the 2 connections on the dynamo what did you connect to the alternator connections?

I must admit you sound as if you have done it but I am a bit worried about the brown and green wire? Where is this connected at the alternator end?
Robert (Bob) Midget Turbo

As Dave, and from my photo (above)- Ive connected the thin brown/yellow and the thin brown / green together, then connected the three thick wires together (as Dave), plus the two thin blue / brown wires that dave doesn't seem to have.

I dont suppose this is helping much ......
S G Macfarlane

Well thats right S.G.
the 71 car had brown wires with a blue trace whilst the later 72 car had these replaced by solid brown on the later regulator. So I suspect that Dave's car is the later control box and car which fits with the "L" reg.
Robert (Bob) Midget Turbo

Hi Robert, SG,
I do have a three bobbin regulator. Two with thick windings and one with thin winding (I think) wrapped in paper/card.
I don't have any brown/blue wires.
I didn't have much option with regards to the alternator connections as the small connector went on the small spade and the large one... well you can guess.
I still have to fit a proper connector on the loom for the alternator and add a thick wire from the third terminal on the alternator to the battery/soloniod terminal. But I want to make sure it is wired correctly first.
Thanks for your help.
Dave Brown

OK Dave

The brown with green trace should connect to the large terminal on the alternator and ill then connect to the 2 brown wires at the reg end

The brown and yellow should go to the small terminal on the alternator and this will connect to the brown and yellow wire that was originally connected to W on the reg.

Then all you need is the duplicate wire from the large terminal on the alt to the positive on the battery, (this is normally connected via the solenoid terminal that has the large battery cable connected to it from the battery.

I hope this helps as I am now setting off on holiday for a week so will not be able to help. Best of luck!
Robert (Bob) Midget Turbo

Hi Robert,
I think I have done it wrong then as I have connected the thin wire from the alternator (Brown Green I think) to the thin wire from the regulator (Brown Yellow I think). I cannot remember which terminal it came from on the regulator but I will check when I get home.
Have a good Christmas.
Dave Brown

This thread was discussed between 18/12/2011 and 20/12/2011

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