Alternator wiring

[peaktorque]

The alternator in my TVR (350i) isn't the correct one for the car (it came free with the engine).

It is a Lucas LRA407 (AFCL) from a Range Rover, no other info on it and the terminals are not marked. There is plenty of info on Lucas ACR units but not this.

I have it wired in a manner of which it charges/regulates 14v, but it is not right as it gets warm and drains the battery when the car is switched off. I also can't connect the battery/exciter lead as one of the two live cables connects to it.

The alternator has two main terminals one bigger than the other. On the correct alternator for the car (Lucas A133-65) the two main wires connect together on the main fat terminal and the exciter on the small terminal. I also have a link wire from one of the main cables with a spade connector on the end which I have no reference to but there is a matching spare terminal on the alt. which it fits. If I wire it up this way the charging light stays on and no charging at all.

The only way to get it charging is to put one of the main wires on the small post and the other onto the larger, the separate spade terminal also has to be connected. No other combination of wiring will work.

What am I doing wrong? Or am I flogging a dead horse and should just get the right alternator for the car?
(I can't see why it couldn't be made to work, but it's doing my very small brain in!)

Thanks

[Steve_D]

You first need to identify from your circuit diagram what and where your existing wires go to as without that there is no way of knowing where they should connect if at all. Are any of them live with ignition off or on?

Steve

[peaktorque]

Thanks,

I removed the alternator and took the plastic cover off of the back and found the terminals marked on the voltage regulator, which are S, B+, IND, D-

I have a permanent live to both S and B+, IND goes to my dash light and D- is the surpressor.

The only way I can get it to charge is to link S to B+ with a fly lead. The dash light stays on if they are not bridged.

I'm thinking that it is wired right but there is a fault within the alternator?

[peaktorque]

This is a pic of it:-



Thick (live) wires to larger post, dash light wire to smaller post, and live wire to spade connector (linked to thicker wires). To get it to charge I need to get a live feed onto the IND (smaller post), the dash light will also go out.

[GreenV8S]

Can't follow through what you've connected to what, but you should usually have:

High current output from alt to battery, also to main power distribution board.
Low current voltage sensing wire from alt to battery.
Exciter circuit connected to a switched ignition feed which is earthed when the ignition is off and connected to battery +ve when the ignition is on. This should go via the no-charge warning light.

There may be additional connections to capacitors for electrical noise suppression, the alt will work with these off.

Suggest you identify the second and third connections and make sure you have switched ignition to the correct one.

[peaktorque]

GreenV8S said:

Exciter circuit connected to a switched ignition feed which is earthed when the ignition is off and connected to battery +ve when the ignition is on. This should go via the no-charge warning light.

I think that maybe this is the problem. The switched ignition is not live when switched on.

The light will come on and stay on (hence no charge) if I don't apply 12v.

I'm now pretty confident that it is wired correctly, just need to ascertain as to why I'm not getting 'excited'

Thanks

James

[InRong Ghia]

This link seems to have lots of useful information, it may help

Motorboat Electrics

[peaktorque]

InRong Ghia said:

This link seems to have lots of useful information, it may help

Motorboat Electrics

Thanks, great find.

Seems that my regulator is failing to 'excite' my alternator.

Ignition on, there is 2v supplied from the dash lamp to the IND terminal, need to find out if that sounds normal.......