Alternator draining battery through aux output.

[TheChrisLeonard]

Hello,

I have a 2017 coyote engine with an xtremex ecu. I have aux output 6 outputted to control my alternator. The battery is draining through the alternator if i have the control plug in and when i check the aux 6 it stays around .3v with the ignition off. Is there a way to stop this or is this normal? The car charges fine with no alternator control attached but i would like to keep it since its available. 

[Adamw]

Aux outputs have a flywheeling diode on them so that will potentially backfeed to battery if there is a pull-up in the alternator and that pin stays alive after Ign off.  However I would have expected most alternators wouldnt be sending voltage out of that wire with ign off.  If you unplug the ecu, what voltage do you have on that alt control signal wire?  Is the alternator "IG pin" definitely not powered with ign off?  

[TheChrisLeonard]

So i measured everything with the alternator unplugged. Its really difficult to get in there with the alt plugged in but i can try to get in there. With the car running i was seeing around 10 amps from the aux out and with the car off and ignition off i’m getting .3v from the aux out. I only have that one wire going to the alternator on pin two and the ring terminal. Here is the connector pinout for it. 

[Adamw]

What I want to know is what voltage is present on the alternator pin 2 with the ign off when not connected to the ecu.  You can either unplug the ecu and check at that end of the loom or unplug at the alternator end and measure there.