94 impreza not starting

[A Doc]

hi guys,

my car wouldnt start and i got te bettery tested, apparentlky it was crap so
i bought a new one. The car started fine, so i shut it off, now this morning
the BRAND NEW BATTERY is completely drained. Any ideas as to what could be
drawing that much power with being noticable?

TIA, alex

 

[mulder]

Are you sure the new battery was fully charged when you got it? Usually
they are sold charged but sometimes they aren't. It's possible it had
enough surface charge to start the car but then it drained off.
Aside from that, with the battery properly charged and installed back in
the car, first check the obvious things such as lights that don't turn
off. Especially check the trunk light which can remain on and not be
noticed. Also look at the parking light switch on the steering column
(assuming this is a current or recent vintage Subaru) to be sure you
haven't accidentally left the parking lights turned on. If you can't
find any lights causing the problem, you'll need to check further for
excessive parasitic drain. Disconnect one of the battery leads and
insert an ammeter, or a multimeter set to measure current, in series
between the cable and battery post. With the car in its normal resting
state (key out, doors closed) you should see a drain well under 100
milliamps. If it's more than that, look for circuits that are energized
all the time (full time 12V) and disconnect things one by one, until you
find the circuit with the most drain. Then look at the individual items

 

[johninKY]

Diode inside the alternator probably failing, allowing the battery to
discharge through the alternator.