Alternator 5-wire: What do G & F terminals do?

[jamiesibley]

On the 2g's the alternator has 5 terminals:
B - to the battery
S - sense wire
L - dash light input/output
and 2 more:

F and G, both go into the ecu. WHAT ON EARTH DO THEY DO?
The 1g's managed to do fine without them, but the 2g's just had to be differant.

I assume the ecu uses them to control power output during differant driving conditions, but what are the exact functions of each wire?

I'm building a new ecu and need to know what they are for, otherwise I'll just throw in a 1g alternator and be done with it.

Thanks

Jamie

 

[Signalgst]

Have no idea how much time i have been wondering the same thing, i`m already using a 1g alternator in a 2g it seems that it something about a powertrain module, don`t know what the hell is that, would love to know....

 

[LightningGSX]

They are used by the ECU to sense and control load on the alt.Mostly to smooth out idle rpms

 

[snox135]

I do know that the 2g alt does not start charging untill 2,500 rpm's. So maybe they have something to do with that?

 

[LightningGSX]

I do know that the 2g alt does not start charging untill 2,500 rpm's. So maybe they have something to do with that?

The alternator definately starts charging before 2500 rpms.LIke I said, the Fr and G terminals are used by the ecu to sense load and control voltage.The Fr is used to sense load.And the G is used by the ECU to control the output voltage between 12.3v-14.4v.When a load is sensed, the ECU will prevent current from flowing, until the RPMs are increased to prevent RPMs from fluctuating.

 

[snox135]

Have you ever checked it? Because I have and it does not charge before 2.5k. Yes it was a brand new Mitsu alternator and I've checked others as well.

 

[LightningGSX]

Yes I have checked it.So your telling me, if you let a 2g idle for long enough, the battery will go dead?

 

[snox135]

If you have checked it there is no reason to ask me that question. There are lots of Japan cars that have alternator likes this. They also use these alternators on Nextel Cup cars because they have this feature. Why they like this feature is beyond me but if you really want to know I can find out.

 

[LightningGSX]

Mitsubishi must be wrong about the ECU they designed then? According to their 2G tech manual this is not the case.

 

[leakyfaucet]

I do know that the 2g alt does not start charging untill 2,500 rpm's. So maybe they have something to do with that?

Absolutely not. The lights would dim at idle. People's batteries would die monthly. People with underdrive pullies would have to cruise at 5000 RPM.

 

[snox135]

Go check it once. It does and there many others that do it also. Maybe the ECU can make it start charging before that if it needs, I don't know. But quit posting stuff you don't know is true without testing it. I have tested several and none of them did not charge at idle.

 

[Tevenor]

If you have checked it there is no reason to ask me that question. There are lots of Japan cars that have alternator likes this. They also use these alternators on Nextel Cup cars because they have this feature. Why they like this feature is beyond me but if you really want to know I can find out.

Don't compare race built cars that spend most of their life near or at WOT or on a charger to a street driven car.

The amount of charge pushed back to the battery is directly related to the voltage and current draw as decided by the ECU. You may not see much depending on the current draw of the vehicle at idle however the alternator does charge the battery at idle.

And since this has become a "does to/does not" thread, moved.

 

[leakyfaucet]

I have tested several and none of them did not charge at idle.

You just said it doesn't charge until 2500 RPM, now you're saying it does charge at idle? Unless the cars you tested were idling at 2500 RPM, you just contradicted yourself.