Series 1- Alternator wiring

[ChrisC]

It would appear that my Alternator is not charging the battery but I am not too sure why yet so I want to start narrowing down potential problems.

The wiring in the car is all new and logically because the fat brown/white wire is connected from the alternator to the 12v battery terminal that is how the charge reaches the battery...

There are also 2 other wires on the alternator - one is probably a sensor to a warning light - I am not confident though of how they are connecetd up

Can anyone please advise by taking a look at their car? You can see one wire is brown green the other is brown purple and you can see there is a terminal spare but I dont have a wire for that...

Below is a picture

[Heuer]

If you put a voltmeter across the battery with the engine running it should read 14.3v. If you put a voltmeter between the brown +ve and earth it should read ~ 14v depending on revs. If not the diode pack on the alternator is faulty (they don't like heat). If you have an output check the control box - substitution with a known working one is usually the quickest way. Check the wiring to the ammeter (presumably you are still using one?) and the connectors are tight. Again a voltmeter between brown and earth should show 14.3v at tickover. The service manual has a good fault finding process.

Ohh, and while you are at it dump the ammeter and fit a voltmeter as it will help diagnose such problems more quickly.

[ChrisC]

thanks David...

I have indeed dumped the ammeter and fitted a volt meter - thats how I discovered it wasn't charging so its already proved its worth. I'll take the alternator output measurement and go from there

I guess if that works then its probably the alternator control box (4TR thingy)

[1954Etype]

thanks David...

I have indeed dumped the ammeter and fitted a volt meter - thats how I discovered it wasn't charging so its already proved its worth. I'll take the alternator output measurement and go from there

I guess if that works then its probably the alternator control box (4TR thingy)

Chris, the brown and green wire goes onto the 'spare' terminal you have. The one you have it connected to is for a warning light.

[christopher storey]

You need also to check the alternator relay . If this is either miswired, or defunct , you will get no charge delivered irrespective of whether the alternator is delivering charge or not

[1954Etype]

You need also to check the alternator relay . If this is either miswired, or defunct , you will get no charge delivered irrespective of whether the alternator is delivering charge or not

Christopher, where is the alternator relay on the early 4.2?

[1954Etype]

thanks David...

I have indeed dumped the ammeter and fitted a volt meter - thats how I discovered it wasn't charging so its already proved its worth. I'll take the alternator output measurement and go from there

I guess if that works then its probably the alternator control box (4TR thingy)

Chris, the brown and green wire goes onto the 'spare' terminal you have. The one you have it connected to is for a warning light.

Chris,

is there an update? Is it charging now?

Angus

[ChrisC]

Thanks Angus, I have now moved the wire.

Having metered the Alternator output this morning - I find I am only getting 12v from the big brown/white wire so it looks like the diode pack has died.

Chris - I am not aware of there being an Alternator relay unless you mean the 4TR?

[Heuer]

Might be worth considering a more modern alternator rather than messing with the diode pack as the bearings are also probably shot. Just make sure the modern one is not too high an output or you may need to change the wiring. Alternative is an exchange 11AC from SNG.

[PETE V]

Chris

My 1967 S1 4.2 has four wires going to the alternator, one heavyBr/Wh going to the bolt, Br/Gr going to the next spade terminal, then Br/V as shown on your image. but then I have another wire, Br/Y going to the other bolted terminal where you have your B/Gr.
May be a difference or change in later productions.

Regards

[christopher storey]

Christopher, where is the alternator relay on the early 4.2?

Angus : how very interesting . Is there not one? My S2 has one, as I learned the hard way when it burnt out on the way back from France! It is with the other 6 RA relays on the LH upper rail

I rewired my S1 , but never noticed that there was no relay!

[1954Etype]

Christopher, where is the alternator relay on the early 4.2?

Angus : how very interesting . Is there not one? My S2 has one, as I learned the hard way when it burnt out on the way back from France! It is with the other 6 RA relays on the LH upper rail

I rewired my S1 , but never noticed that there was no relay!

Ah ha! The only difference I was aware of on the later cars was the 3AW which detects current from the alternator and keeps the ignition warning light on. Bolted on the bulkhead frame near the heater. (Works in reverse in that it breaks the current when current is detected).

Don't know what a 6RA would do in the relay circuit though.