Could be faulty diodes in the alternator.

Do a search on this forum. There should be plenty of posts about failed diodes.

Some test info: '96 Legacy, EJ22 engine, key off & removed

mA meter between -battery post and post clamp.

65 mA steady current after 1 minute (to let ECU settle down)

= 1.5 Ah/day = 47 Ah/month

Group 35 batteries used in the '96 typically list ~ 40 Ah capacity, so could discharge battery in a month...

Leaving my UltraGauge (OBDII viewer) plugged in doubled the draw - apparently it keeps checking to see if the key has been turned on yet - so only 2 weeks to discharge battery.

Got bitten when I didn't start the car for several weeks followed by a sub-zero cold snap (discharged batteries freeze easily)...

This might help out some. It has helped me learn by watching it be done methodically and competently.

Edited January 13, 20188 yr by Boxer Medic

Wanted to update to possibly save someone else the headache in the future.

 

You definitely NEED BOTH wires going to the alt (constant 12v+

AND the "dummy light" wire

). 12v+ constant *can* be attached to the right-side (if looking down at engine from front of car orientation) terminal and will allow alt to charge but needs a key-on activated relay to avoid draining battery at engine off. After getting both wires in proper orientation and connected, no drain and car can sit w/o being dead overnight.

 

My mistake for thinking they could be run as a 1-wire set up as-is. Connector plug was cut to get the Tribecca alt to work before, and once reverting back to the factory-style alt, saw it was charging with right-side getting fed 12v+ constant and assumed it was correct. Since the drain can take days to leave battery dead to months in warmer weather, and alt was testing OK with good diodes; like chasing a group of wild turkeys.

Edited February 11, 20188 yr by Bushwick