The 'E' Type Forum

On my 3.8 the dynamo is replaced with a compact alternator but without any built-in voltage regulator.
I plan on fitting a 4TR voltage regulator instead of a RB340, and the new wiring loom is for a car with the RB340.
Surely this has been done by many around before, but could not find any thread relating the process. So seeking for guidance for this installation.
Thanks in advance!

If it is a modern alternator then it has all the regulation electronics within. Just two wires. Thin one to your ignition light and big thick one to the battery.

If it is an old alternator that has rotor and stator connection then you will need a 4TR type external charge regulator.

As you say your alternator needs a separate reg. The circuit can be copied from a later car. The dynamo has two wires. One thick brown/yellow that carries the charge current (up to 20 or so amps) and a thin brown/green that carries the field winding current (around three amps or so?

The early alternator has four wires. Two are field plus and field minus. F+ goes to the + terminal on the reg box and then on to the ign switch. F- goes to the F terminal on the reg box. The other two are the ignition warning light relay and the fourth is the main charge that goes to the battery via the pretty useless ammeter. You need to replicate this arrangement. My car has the dynamo but I dare say someone with an alternator set up can help. Remember that a dynamo can generate about 20 amps or a bit more. An alternator can generate 40 or 50 amps so the wiring needs to be that bit thicker.

Good luck. J

Thanks Julian,
The alternator I have has indeed 4 connections:
B which is large bolt (guess this goes to the battery), and three spades marked E / F / N. So how to connect these to the 4TR regulator and ignition lamp?
Grateful for any advice.

Hi Ralpe.. lots of info here, viewtopic.php?t=6668

Ralph

I would give serious consideration to putting your alternator on eBay and buying one with an integrated regulator. The 4TR's are notoriously unreliable and although you can carry a spare they sometimes fail in a state that allows over-charging which will destroy your battery. The Nippondenso described in the Upgrades Forum can be bought for about ?50, sometimes less.

If you want to continue it would be good to have make and model number of your unit because those markings are not universal. Looks like E = warning lamp (excitation), F = field, N = neutral and the large terminal is B (battery). You need to map these to the 4TR:


So my guess would be (negative earth obviously):

F to + on 4TR
N to F on 4TR

E to AL on 6AW
B to battery +

Getting it wrong though could destroy the alternator diode pack!

Thanks David, very explanatory.
The actual alternator is a Denso (Kubota), and looks pretty much "period" on the car. It was fitted by the PO in place of the dynamo, but regretfully the wiring loom has been butchered and I could not find out how it was wired and no trace of a regulator.
I am away from home this week, when back will post a pic to illustrate.
But basically, you are entirely right about reliability, and the more I think about it the more I am incline to jump for a modern unit.