Alternator disable switch by disabling the field

[saand]

Hi All,
The next mod on my list is the alternator disable switch. I can easily turn off the output of the alternator just using a relay however there are advantages to just turning off the excitation field.
I attempted this by trying to isolate the field wire that goes into my alternator. So i cut a wire, ran the engine and no success, the voltage on the battery actually went up. So I was a bit confused then after a bit of research i realized this is likely a feedback wire which tells the alternator what voltage the battery is at so that the alternator can alter the excitation field to increase or decrease the charging rate.

I then reconnected this wire and cut another wire, but found the same issue, this may or maynot be the return wire for the voltage sensing.

The only wire left that i can see is the output wire, the positive that goes to the battery to charge it.

Other forum threads have suggested some cars have a dedicated field enable /disable signal however from what i can see so far mine may not have this.

So a question to anyone that knows about disabling the field of an alternator. Is there any way i can interrupt the field without actually opening up the alternator and isolating one of the excitation field brushes.

Thanks

[Piwoslaw]

It is very possible that your alternator is self exciting, as is mine (only one thin wire, disconnecting which doesn't do anything). AXMonster started a great thread (Automatic alternator cut out/regen braking), where got down and dirty with his internal field alternator, but it appears that rewiring the diodes inside wasn't enough It's worth a read, though, and your alt might have a slightly better (= easier to hack) design.