Self reguating alternator

[mach2andy]

For some time now I’ve been bookmarking self regulating alternators that I thought may fit my car. But my recent burnt out alternator relay galvanised me to take the plunge. I ordered this

https://www.ebay.co.uk/itm/324193342893 ... 101224.m-1

and it fitted almost perfectly. I say almost, because I did have to shim the pulley forward by 3mm, but that was it. And this task was simplified by the 8mm allen keyway in the end of the shaft which made removing the pulley securing nut very easy.
So, no modified mounting or adjusting link, and the 6RA, 3AW & 4TR are now history. The connections consist of a group of 3 [ B+ B+ D+ ] for which a Lucas style plug is readily available, and a separate B+ terminal post which has a separate 6mm spade term next to it. The smaller terminal post is, I think, the tacho connection.
Having removed the plug from the 4TR, I linked the brown/yellow & brown/black wires disconnected from the 3AW, and at the alternator connected the brown/yellow wire to the D+ terminal. With the ignition on but the engine stationary, current flows from fuse 7 through the warning light which illuminates. This 12v also provides the initial excitation of the alternator. As the engine starts, the earth that was present at the D+ term is replaced by 12v, and with 12v at either end of the warning light circuit there will be no current flow.
INTERESTING ASIDE.
Having fitted and tested the new alternator, I then replaced the instrument lamps with LED’s. However, the first time I started the car with the LED’s fitted, the ign warning light remained on, and my tester showed only battery voltage. The reason I discovered was that there was only 5v at the brown/yellow wire at the D+ terminal which was obviously insufficient to excite the alternator. Replacing the LED with the original incandescent lamp restored the necessary 12v and cured the problem. Why there is only 5v downstream of the LED I have no idea, but hopefully someone will educate me?
Only time will tell if this unit turns out to be reliable or not, but at £50 it wouldn’t be overly onerous to carry a spare, and the 3 spanners necessary to change it.

[mgcjag]

Nice write up Andy......Steve

[Gfhug]

Ordered

And thanks Andy for doing the research

Geoff

[MarekH]

A conventional filament bulb is not directional and presents a low resistance.

An LED is a type of diode. This presents an infinite resistance in one direction (i.e. current can only flow one way) and a characteristic resistance (or voltage drop) in the other direction.

Essentially, the LED light presents too high a resistance for this circuit, so insufficient current flows into the field coil to get it to produce enough magnetism as the field coil rotates.

kind regards
Marek

[rswaffie]

If you want to use an led for the ignition warning light, you need one of these….
https://www.bettercarlighting.co.uk/ind ... ductId=704

[MarekH]

No you don't.

It is of no value whatsoever to "upgrade" a tiny filament bulb which is only lit for a few seconds per month with something more complicated, which doesn't work any better and which needs to be paid for and installed for the privilege of doing nothing useful whatsoever.

Just send your spare money to me. At least you get good advice in return.

kind regards
Marek

[mgcjag]

[rswaffie]

Marek
I was merely offering a potential solution to the problem that the op noted in his post, related to an upgrade that many on here, and professional restoration companies, choose to apply.
I’m sorry if you feel I wasn’t offering ‘good advice’.

[johnetype]

The connections consist of a group of 3 [ B+ B+ D+ ] for which a Lucas style plug is readily available, and a separate B+ terminal post which has a separate 6mm spade term next to it. The smaller terminal post is, I think, the tacho connection.

Andy, this is a very useful modification which I did on my car three years ago and has proved reliable so far and in my view looks much closer to "period" than the spindly Denso alternator alternative. Very cost effective too. Removing the 4TR and 3AW is a great boost for reliability although you can leave them in place (but unconnected) for visual effect if you like.

To clarify, you can either fit a Lucas style plug connected to B+, B+ and D+ or use the separate B+ post and D+ but you don't have to use both, just make sure to insulate the B+ post as it's always live.

The smaller terminal post is indeed the tacho connection but to be clear that isn't for any of the tacho's used in our cars but mainly used by diesel cars to drive their tachos. It is in fact the same as the AL terminal on the original alternator and could be used for connecting to the 3AW if you're a purist but you'd still have to fit a separate (hidden) ignition warning light to energise the alternator at start up.

[mach2andy]

Thanks all. Apart from wanting to be able to read my instruments at night and in tunnels, one of the reasons that I changed all of my instrument lamps was that I do not want to insinuate my hand up the back of the instrument panel to change any of these lamps ever again. Maybe slightly naive of me I know, but that was my aim. Also, I am I have to admit, slightly OCD when it comes to groups of things all being the same and do spend inordinate amounts of time ferreting around in, for instance, my washer tin trying to find several exactly the same.

If you want to keep your original Lucas 11AC alternator, but want an alternative to the 3AW ign warning lamp arrangement, I think some folks have used one of these............

https://www.improvingclassicmotorcycles ... oducts.htm


I've included this pic of the alternator belt fitted to my car in case you want to achieve the same position of your replacement alternator.