Field wire from alternator when upgrading from 3 pin to 4pin

[Adzn3k]

Hi people, 

In my engine swap the alternator is dying a slow death and I'm looking to upgrade. My particular toyota engine came with 2 types of alternator in its time a 3 pin and later in a 4 pin higher output unit.

 

I currently have the 3 pin and I'm looking to change to the 4 pin version, my issue is what do I do with the extra "field" wire? I'm struggling to find any solid info online as to what to do with it, some places say to just ground it out and others say it needs to be connected to the ecu. 

Is there anyone that can point me in the right direction? 

 

Cheers 

[Vaughan]

Which engine and car do you have?

[Adzn3k]

5 hours ago, Vaughan said:

Which engine and car do you have?

It's a 2az fe in a celica gt4 

[Vaughan]

I haven't dealt with that particular engine/alternator but I suspect it is some form of voltage control for efficiency purposes.

There are two options for the type of control, either different defined levels regulated by the alternator and defined by the ECU or the ECU needs to output a PWM signal which it is constantly updating to control the alternator output voltage (ECU is doing the regulating control).

The info I've found online suggests that the ECU is doing the regulating so you will need to figure out what frequency the signal is, wire that alternator pin to a spare pwm Aux and then setup some form of control loop for it in the ECU.

An Alternator Control function is coming for G4X but there are ways to control them with existing firmware as specified here 

Looks like you've found this forum post which talks about the 2GR alternator which I would expect to be identical in operation to the 2az 

 

http://toyota.aitnet.org/Toyota/Camry/Camry_2007_wiring_diagrams.pdf