Alternator Wiring

[Cerberus90]

The two thick wires coming from the alternator.

Without the 'distribution blocks' on the bulkhead, due to custom fusebox.

Can the two thick wires from alternator both be connected to the starter solenoid, with a feed from the battery coming to the same point on the solenoid?

If not, how is best to wire the alternator up with a non-standard fusebox/wiring system?

[oldgeebee]

Cerberus90 said:

Can the two thick wires from alternator both be connected to the starter solenoid, with a feed from the battery coming to the same point on the solenoid?

In theory, yes. One of the wires is for charging the battery the other is to sense the voltage to regulate the charging current. In practice, you might have trouble connecting so many large wires to the starter solenoid since there are usually also a couple of thick wires from the solenoid to feed the main circuits. On my car (3000S) the sense wire is connected through a fuse to the battery feed which serves all the 12V un-switched circuits through a 35A fuse. The charging wire is connected at the fuse box (un-fused) with the battery feed wires from the starter solenoid.

HTH,

GB

[ausi steve]

Firstly are both the thick wires alive? Usually only one is alive & the second thick wire is a feed that picks up off the alternator battery terminal to supply other live battery feeds in the car.
Most alternators have a built in regulator, they sense from internally.
The thin wire to the alternator is from the ign warning light, it has two purposes, one to excite the alt to allow it to start charging, the other to turn off the ign light once the alt is charging.

[Cerberus90]

Having had another look at the alternator plug in the old loom, it would seem that both thick wires just went up to the distribution block to the same pin. Then I think there's a thick wire from there to the starter solenoid.

Is it possible to test if one wire is alt charging live, and the other just a pick-up?

Think we're going to use one of these to allow feeds to be distributed easily.


As for the ign light. I'm trying to follow the TVR wiring diagram, so I've got a fused feed (ign switched) coming in, which feeds the tacho, volt meter and voltage stabiliser and then to the ign light bulb, then to the thin wire on the alt plug.
I presume that thin wire on the alt, once the alt starts charging, cuts the earth off, so the ign light bulb goes off. And when not charging, there's an earth through it which causes the light to come on?

[oldgeebee]

Cerberus90 said:

Is it possible to test if one wire is alt charging live, and the other just a pick-up?

I think I may have given you a bum steer on the sensing wire - the ACR series of alternators have got internal sensing so that both output terminals can be used for battery charging. You can check this by looking to see if the 2 large terminals are connected together.

Cerberus90 said:

As for the ign light. I'm trying to follow the TVR wiring diagram, so I've got a fused feed (ign switched) coming in, which feeds the tacho, volt meter and voltage stabiliser and then to the ign light bulb, then to the thin wire on the alt plug.
I presume that thin wire on the alt, once the alt starts charging, cuts the earth off, so the ign light bulb goes off. And when not charging, there's an earth through it which causes the light to come on?

Almost - the small terminal provides an earth when the alternator isn't turning and then 12V once the alternator is generating an output voltage. With one side of the ignition light connected to the switched 12V and the other to the small terminal on the alternator the lamp lights unless the alternator is producing 12V.

GB