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2000 Subaru Impreza Outback Sport Wagon
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Discussion Starter · #1 ·
I'm chasing down a sporadic parasitic draw. The battery is usually okay for a few days, but occasionally drains below cranking capacity within a day. I had the battery and the alternator tested at a shop, and told both were fine.

I did a basic voltage test. Starting with a healthy battery (12.6v), turning the car on gives a measurement of 13.6v or so at the terminals. As soon as I add load (lights and fans,) that drops to 12.2-12.4v. Would this mean anything? Is it a bad ground? A dying alternator?

Also, I recently noticed the auto-lock feature after getting inside the car sounded strange. I think it's coming from the door panels or somewhere in the dash but the locking mechanism can be whiny and slower. The car came with a Compustar remote entry and alarm. The fuse for the alarm had to be pulled (was malfunctioning to engage alarm), but the remote has been working fine. Would the remain of the system cause this?

Aside, I wanted to rule out 2 basic things. I'm hoping someone can chime in or show me comparison pics from their cars.

Fuse box: Am I missing the relays? Would those affect the drain?

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Alternator: Is the metal piece at the end of the long bolt placed correctly? Is there anything I should watch for or clean up when mounting the alternator? I'm worried I messed something here when I pulled the belt shroud while back.

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Anyways, any advice in how to proceed or what to look for would be super helpful!
 

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There could be a parasitic draw but you would have to hook up the meter in line with the battery and check how many amps it is drawing when the car is at rest. Usually have to wait a bit for the modules to go to sleep and make sure you mimic everything as if the car is shut off and door closed to not cause unnecessary current flow to systems that shouldn’t when the car is off like door jam sensors are pushed in and etc. Typically should probably draw no more than 50mA.

I believe there should be relays there since my RS also had relays/fuses there from what I remember. Doubt this is what is causing any type of draw since you would be creating an open with nothing plugged in but there might be electrical gremlins within the system.

Alternator bracket is normal. I would try to do a voltage drop test on both ground and power side of the alternator to see if you are losing voltage on either side of the circuit. I had a .5v loss on the ground side of my alternator causing the circuit to not charge at all. I am guessing mines was probably due to corrosion causing resistance between alternator and engine ground. I regrounded the alternator bracket directly to the battery and everything works fine now, battery light turns on and alternator charges around high 13v~low 14v when car is on.

Information on these two test is readily available online. Just look up how to do them and perform and see what results you get but I would start with voltage drop first.
 

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Any aftermarket electrical systems would be my first suspicion to a parasitic draw. A dying alternator or poor/corroded connection with the battery terminals could also be the case. In my experience a lot of the time it's something simple and stupid that is causing minor issues.
 

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If I remember right, the parenthesis'd relays/fuses are optional equipment. Alternator bracket is correct, you would know if it was wrong.. it doesn't fit.

Only do this with the car off, do not cycle the key or you will blow up your multimeter: Disconnect the negative cable from the battery, put your meter on the 10amp mode and place it inline of the negative clamp, and the negative post on the battery. This will show you how much parasitic draw you have. .5 to less than 1amp is ideal. If you notice more than 1 amp draw, start removing fuses til the draw goes down to 1 or less, that's your problem circuit. I'd start with unplugging whatever is left of the alarm system.
 

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2000 Subaru Impreza Outback Sport Wagon
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Discussion Starter · #5 ·
Thank you everyone for the input! Really appreciate the time you took in reading and replying.
Since the car has been running fine without those relays, I'll leave that as is for now.


I did the amp tests. Draw was around 0.080 to 0.086A. (=80mA range) Some fuses like the clock, radio, AC affected the amp reading down to 0.062A momentarily but after fluctuating, it always ended around 0.080A. I didn’t find a fuse that clearly dropped the reading. I found Compustar CM7200 (module running my remote) jammed in by the pedals. I'm gonna trace down its fuses tomorrow, and see how much that is contributing to the 80mA.

I also did an another test (referring to a video by Humble Mechanic on YT) and measured voltage at the fuses. All the fuses dropped to 0.00v after showing initial spikes. Again, nothing seemed suspicious.

I ran out of time but did briefly test the alternator. Since I knew it was struggling to keep up with charging with load, I sanded down the nut-bracket (what I pointed to in the previous image) and tightened the belt a little. That seemed to help a little. From the negative terminal to the alternator case measured -130mv (= 0.13v.) ? Isn't 0.13v too high? I'm planning to clean all contacts on the alternator and locate the grounds, and redo this test.

Is there anything I'm missing? Also where is the body ground in an EJ222? And are all the grounds accessible from the engine bay?
 

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I haven't gotten my hands dirty on too many ej22's but i know the 251's were grounded from the firewall to the rear left of the intake manifold by the brake booster fitting, and then the passenger strut tower to one of the power steering line bracket bolts.
 

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I had a parasitic draw as well, for years! Took forever to narrow down the cause but turns out it was a defective, rebuild Napa starter. It was always drawing a little bit to some power, even when the car was off. (It's wired directly to the battery after all)

Thanks to RockAuto, I no longer have to rely or those rebuild starters. Got a new one from them and car's been fine that way since. Even my voltmeter is reading slightly more correctly! haha
 

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Discussion Starter · #8 ·
So today, I took out the alternator and sanded/cleaned all the contacts. I'm pretty sure it's the factory unit. While the belt was changed last year, the contacts looked flaky and I have no idea when it was last taken out of its spot.

After cleaning, I saw significant improvements:

Car on (no load): 14.12v
Car on (w/ load): 13.98-14.00v
Negative terminal to alternator case: -28 to -30mv (0.03v)
Negative terminal to engine ground (driver side, below throttle cables): -36mv (0.036v)
Positive terminal to alternator b+ post 110mv (0.11v)

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I'm leaving the battery connected and will see if the car still cranks tomorrow. Was the poor connection causing the battery to not recharge properly or was it draining the system while the car was off?

I think I found the body ground behind the air filter box, by the firewall. It dangles down to the transmission. I think my next move would be to clean this ground and check the starter connections. I don't know if my starter is original, but something occasionally make a buzzing noise at ignition. (though I think the noise maybe the power steering o-ring)
 

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Discussion Starter · #9 ·
Leaving it overnight, the battery is usually in the 12.36-12.40v range. It cranks fine so that's better but still seems like quite a big loss. I doubt it can sit longer.

@clsmooth May I ask how you found out that the starter was the issue in your case? Was it just from swapping it or did you run any tests to confirm it was draining power?
 

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Normal for a battery to settle in around the 12.3-12.4 range after sitting. I would disconnect the battery overnight and get a comparison to the above numbers, I have seen failing batteries drain with no load at all due to an internal failure.
 

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Discussion Starter · #11 ·
I've been disconnecting the battery most of the time after driving. Voltage is usually in the 12.3-5v range after few days and cranks fine. I installed this battery around May, and while several draining cycles may have hurt it, I'm hoping I can rule it out.

Anyways, I found out one of the 30amp fuses wired to the CM7200 brain (remote entry/alarm module) had a voltage drop of 0.1mv. I'm planning to do an amp draw test again, and maybe have this fuse pulled to and see its effect to the battery.
 

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Are you reading milliamps or millivolts? .1 milliamp draw will drain the battery over a week or two. I've found 50 milliamps is about as much as you want to see on our early Subaru vehicles, which is equal to 0.05 amps. Newer vehicles with ECUs, BCMs, multiple door modules and such running in the background, .008 is common. We shouldn't see those numbers on our cars.

.1 millivolt would be a 10th of an amp, that's what I would expect to see with a glove box light or smaller constand draw to read. While you are performing a current draw check, try pulling the clock/backup fuse, only a few circuits in your car that are running (clock, radio memory, etc).
 
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