alternator wiring help

[finyuk2005]

Anyone good with alternators?!
Got a new one to stick on the perkins powered fermec 860 digger, but its a bit different to the old one.

Old one had a 3 pin connector plus a small wire with a ring terminal.
I figured 2 of the pins are both heavier wires that go to the positive on the starter, the other pin on that connector is a smaller wire, that is a switched ignition live,
The other small wire with the ring terminal i was presuming is the W terminal for the tacho? Strangely though that was attached to a post on the old alternator stamped B+ which i thought was usually battery positive?
The new alternator has 3 posts and another spade terminal, but nothing is marked!
I think from google lensing it, the 3 posts are battery positive on the left, switched live/charging light in the middle and the W on the right,

any thoughts?!
cheers

 

[m_c]

That classic 3 pin connector, the two heavy spades go to battery (however depending on the exact spec of alternator, some had only 1 as an output, and the other as a battery sense, whereas others they were simple paralleled), and the small spade the warning lamp (that was always consistent).
The W is for the tacho, but some alternators used a generic casing, so although the casting says B+, it's likely a W terminal.

As for the new one, only guaranteed thing is the B+, which will be the biggest stud.
To find the warning lamp terminal, easiest option is to probably fit it, and connect a test bulb (needs to be at least 2.2W!) to see if any light up the bulb, and then causes the alternator to start charging.
Once it's charging, run over the remaining two terminals with a multimeter on VAC (or Hertz if so equipped) to see what one is outputting an AC signal (the W is just a raw pre-rectifier feed from a phase).

Then you might find the remaining terminal is a battery sense feed.

 

[finyuk2005]

That classic 3 pin connector, the two heavy spades go to battery (however depending on the exact spec of alternator, some had only 1 as an output, and the other as a battery sense, whereas others they were simple paralleled), and the small spade the warning lamp (that was always consistent).
The W is for the tacho, but some alternators used a generic casing, so although the casting says B+, it's likely a W terminal.

As for the new one, only guaranteed thing is the B+, which will be the biggest stud.
To find the warning lamp terminal, easiest option is to probably fit it, and connect a test bulb (needs to be at least 2.2W!) to see if any light up the bulb, and then causes the alternator to start charging.
Once it's charging, run over the remaining two terminals with a multimeter on VAC (or Hertz if so equipped) to see what one is outputting an AC signal (the W is just a raw pre-rectifier feed from a phase).

Then you might find the remaining terminal is a battery sense feed.

thats brilliant thanks!
the two heavy spade lugs are joined together on the alternator,
Also good to know the casings are sometimes generic, i have a feeling thats the case here indeed!
I'll see how i get on tomorrow,
cheers!

 

[finyuk2005]

Got the digger going today,
new starter, alternator, battery isolator and all new cables, and shes like a new machine!! apart from the rotten cab, and the 4wd that doesnt work, and the brakes that recently failed...! but she starts instantly

i had to swap the pulleys on the alternator and noticed the fan on the old one.. looks odd, why would it be like this i wonder?!

 

[m_c]

If you look at most modern cooling fans, they're not symmetrical.
It's to do with aerodynamics and sound.

 

[finyuk2005]

If you look at most modern cooling fans, they're not symmetrical.
It's to do with aerodynamics and sound.

ah ok interesting!
cheers