Alternator wiring question

[f_inscreenname]

Built a couple motors for a boat I rebuilding and have run across an wiring issue.
Due to money getting short I plan on using (if possible) the original #807653 Mercruiser Alt?s. They have 4 wires (as in the picture). A ground and a hot wire but they also have these two wires marked with red arrows. Wire ignition terminal and Wire Battery sense. What do they do and are they needed?

oops:redface:

 

[Don S]

Re: Alternator wiring question

No picture ???????

 

[f_inscreenname]

Re: Alternator wiring question

oops
fixed :redface:

 

[Don S]

Re: Alternator wiring question

Yes, they are needed, without them, the alternator will not charge. They are hooked to the regulator.

 

[f_inscreenname]

Re: Alternator wiring question

Thanks Don
Looks like I'm looking for parts.

 

[Don S]

Re: Alternator wiring question

What parts?

 

[f_inscreenname]

Re: Alternator wiring question

What parts?

I don't have regulators on these stripped 454s and the wiring in the boat is set up for single wire so something has to change.

 

[Don S]

Re: Alternator wiring question

The regulator is built into the alternator, that's what those two wires are attached to. All you need to do is add some wiring, very minor amount really.

Basically, the purple wire hooks to any purple wire coming from the engine harness. BEFORE it gets to the ignition which may or may not have a resistor wire or ballast resistor.
The red one can go directly to the main battery terminal on the starter solenoid along with the main battery cable.

 

[f_inscreenname]

Re: Alternator wiring question

The regulator is built into the alternator, that's what those two wires are attached to. All you need to do is add some wiring, very minor amount really.

Basically, the purple wire hooks to any purple wire coming from the engine harness. BEFORE it gets to the ignition which may or may not have a resistor wire or ballast resistor.
The red one can go directly to the main battery terminal on the starter solenoid along with the main battery cable.

Thanks Don
Where does the "any purple wire" come from? The boat doesn't have a mercruiser wiring harness.

 

[Don S]

Re: Alternator wiring question

The purple wire comes from the ignition switch, and is the one that puts power to the + terminal of the coil.
What type ignition system are you going to be using? Are you planning on makeing your own wiring harnesses?

 

[f_inscreenname]

Re: Alternator wiring question

The purple wire comes from the ignition switch, and is the one that puts power to the + terminal of the coil.
What type ignition system are you going to be using? Are you planning on makeing your own wiring harnesses?

It's a MSD system with magnetic distributor The system is pretty self contained. Just power the box and its wiring harness does the rest including the coil.
So basically the purple wire is a switched wire thats hot when the key is on?

 

[Bondo]

Re: Alternator wiring question

So basically the purple wire is a switched wire thats hot when the key is on?

Yes,...

 

[f_inscreenname]

Re: Alternator wiring question

And it wont back feed the system right?

I herd that from someone a while back.

 

[Don S]

Re: Alternator wiring question

Merc and Volvo both use that same alternator, and hooked up the same way. It's how they are hooked up, just like it shows in your picture.

 

[f_inscreenname]

Re: Alternator wiring question

Got ya
Thanks guys.