Possible current leak with ignition off?

Hi, First thing to do is clean out the engine bay with degreaser. Pick a sunny day and power wash and dry out.

Dunno where you live but here in the south - 2.5 to 3 years is about average for a battery.

wait, somewhere ther's a map.....

I heard that maintainable batteries were often preferred in hot climates. Something about maybe getting a year more out of a battery that would otherwise be lost via evaporation of the water. I do live in a mild climate although occasionally I've taken it to hot climates.

So I went out to Costco and bought a new one. Not maintainable like the OEM battery, but I'm not sure where to find one. Starts well.

I'm still not quite sure why it went from working well to just dying. Maybe one time too many where the map light was left on overnight.

Heat does kill off batteries, that's why some cars now have heat shielding or venting for airflow around the battery. But, that's only in some cases and uses (one is Ford Crown Vics with the full police interceptor package) where the underhood temperature is excessive to start with.

I racked my brain for something solid to back this up, as I remember seeing 150-200 deg F (somewhere in my past) as somewhat normal underhood temperature, with "excessive" starting at 200. Unfortunately, my Google-Fu isn't working well tonite, I couldn't find a website cite to back that up.

But I did find this little gem: (well worth saving on your hard drive, it's less than 6 mb)

Same author cites a test done by Johnson Controls that found the average life of a "good quality" battery is 37 months.

That same PDF has a section on why and how batteries fail, but it's a little bit too technical in some ways and misses some basics.

Assuming that the charging systems is OK, most "just overnite" battery failures are individual cell failures. When the battery gradually fails, it's degradation of most or all of the cells. The PDF explains failure conditions well but didn't really explain 'that' difference well.

A 12 volt battery is 6 individual 2 volt cells connected "head to tail" (series) to total 12 volts. Each cell has to be in good working condition for the whole battery to work. It's like those Xmas tree lights that if one bulb burns out, the whole string's dead, or the chain is only as strong as its weakest link.

"Mindfarts" do that. Been dere, dun dat. My (un)favorite is sitting in the car, listening to the stereo with the key in ACC, then turning the key to ON to open the power window to talk to someone, and forgetting to turn the switch back to ACC. Damned DRLs (daytime running lights) do drain the battery fast!

If it does it most of the time, I'd disconnect the battery overnight for a couple of days to see if the problem happens at that time as well.Should the problem not go away, the battery is clearly the problem. Should it go away, perhaps leave the battery connected and start pulling different fuses overnight: If you have 20 fuses, start with pulling 10. Determine whether the left in fuses of the fuses pulled were the problem. The second day pull 5 of the ones at fault, leaving the other five in. The third day, pull out three, leaving two in, Etc. Once you determine what leg causes it, concentrate on all things that are hooked to it. I'd start pulling the fuses that all lights hook into.

I realize that you have remedied the problem, but I'm sure others will have this problem and might come across this thread. I like the fuse pulling scheme. I have a quicker variance of that method though. Use a multimeter (they're less than 10 bucks at most autoparts stores.) and measure the current across all of your fuses. Some of them should have current when the car is off, like the one going to the clock, or if you have the door open while doing it, the one to the dome light. But any fuses that have current going through them are on suspect circuits. Tracking down shorts from there can still be difficult, but at least you know what circuit it is on. You have to pull the fuse and put the leads across the gap that the fuse occupied, or one in each hole that the blades of the fuse go into.

I have a cheap digital multimeter. You almost make it sound like the movie "Apollo 13" where they're trying to determine the least amount of power they can get away with using to get back, using an identical rig on the ground. Being an engineer, the one thing I didn't understand was whether or not they compensated for any temperature differences that could lead to decreased current draw.

Again - I have the suspicion that it was just a weak battery that finally gave up after 5-1/2 years. My other thought was that it was a dying starter (where a charged battery might mask the symptoms), although that wouldn't explain the weak sound of the "finder" indicator after the car had been sitting for a few hours. It started fine with a portable battery-powered jump starter (these things are great) but after a while it gets inconvenient if you need it every other start. The electrolyte level was fine, but I'm not sure if that matters much after 5+ years.

While all this discussion of battery life is valid, I think it's a red herring. The fact that your odo diplays remain on indicates that there's a current draw with the key off. The LCD displays themselves are too low to be the problem, but they're not on a dedicated circuit. Remco has the right idea. Find out what else is on that circuit and you'll find something else that's sapping your power.

I might start by simply looking for the most common culprit;

- trunk light on all the time.

Open the trunk, find and manipulate the trunk light switch and verify the bulb goes off when the switch is opened (i.e. in the position it would be when the trunk is closed).

Assuming it's not the "Subaru-Virgin" switch....

If it does it most of the time, I'd disconnect the battery overnight for a couple of days to see if the problem happens at that time as well.Should the problem not go away, the battery is clearly the problem. Should it go away, perhaps leave the battery connected and start pulling different fuses overnight: If you have 20 fuses, start with pulling 10. Determine whether the left in fuses of the fuses pulled were the problem. The second day pull 5 of the ones at fault, leaving the other five in. The third day, pull out three, leaving two in, Etc. Once you determine what leg causes it, concentrate on all things that are hooked to it. I'd start pulling the fuses that all lights hook into.

I started looking for photos of Impreza and WRX instrument clusters with the ignition off. They all show the LCD display for the panel on but with the backlight off; the backlight turns on with the ignition in the on position. I guess the 2002-3 models had the speedometer in the middle (along with the odo) while the 2004 model moved it to the right. I also might have been confused since I've been driving a Honda Civic, and that one shuts off its LCD display with the ignition in the off or accessory position.

I will check though. However - I'm finding that everything looks good. After 5-1/2 years I think the old car was about ready for a new battery.

Quite familiar with that. I keep around sets of AA rechargeable batteries for use in a camera. Some sets are unusable after a day, and I can trace it to one or two of the individual cells suffering a rapid demise.

I thought that series lighting was a thing of the past. It would require higher voltage and of course there is the problem you mention. I think most string lighting systems now just tap into two power and ground wires.

Let me just say that it's not usually me leaving the map light on. However - I was the one who thought that the parking light left on overnight wouldn't be a problem. That prompted me to get a portable jump starter after someone helped jump my car with one.

My 1990 Mustang blew an alternator 150 miles from home (at night), so I had Ford put in a rebuilt alternator (they had no new ones - bad idea, should have driven home in the morning without an alternator).

The new alternator had a short of some kind in one of the windings (probably solder), so on random days my battery would be dead in the morning. I took it in to a local Ford dealership, and they yanked out the perfectly good hatch light switch (there is no trunk), and charged me $100 to not fix the problem. A few weeks later when the short was gone, I replaced the perfectly fine hatch switch.

Beware of things you do not expect, and things which seem to be the problem but are not.

The fuse box Ammeter (DVM, etc) idea is GREAT, but be careful about your assumptions. The short may not be fused! The alternator and the voltage regulator for example are not fused.

After a few weeks the short burned itself out, without frying any diodes, and all was well until that alternator blew a diode a year later. Replacing the factory High Output (!!!) 65A alt. with a brand new Ford 100A alt. solved the diode blowing issue.

I suggest starting this procedure by disconnecting one battery lead, and connecting the DVM across the gap. Do this with EVERYTHING turned off, and the meter set on DC Amps. This will tell you the total draw, which should be very small, but is probably close to 1 Amp if it kills your battery overnight. Then if you find a 30 mA draw on a fuse, you know that is not the problem. At that point I would ignore anything below 100ma on any one fuse. (1000 mA =3D 1 Amp). You must do this with a fully charged battery.

Do not forget to reset your computer and FI system after screwing with the battery connections. I did once, and it trashed my injectors a few days later with a backfire (that can't happen, I know - but it did).