Author Topic: Electrical car issue (Read 2022 times)

sumpnz · « **on:** June 25, 2020, 12:04:34 AM »

2010 Subaru Forester we bought from a co-worker back in March is having electrical problems. Thought it was a bad battery (still had factory original battery). Put in a brand spanking new battery with a June 2020 manufacturer date. It started just fine. Ran it for about 30 seconds and shut it down. Made sure everything was turned off. Went to go drive it today (yay! I'm allowed to drive again!) and it was deader than a door nail.

Got a voltmeter and it was showing 8.3V. Yikes. Looked for a loan and with the battery disconnected figured just for grins I'd look at battery voltage again. 13.7. Huh. Weird. A bit later looked again. 15.1V.

Ok. So something is putting a BIG load on the battery. Question is, what?

A friend is going to send up a trickle charger and a good multi-meter. Figure it'll take probably a day to 2 days to charge it, but once charged I can do a parasite load test.

Until then do you all have any (useful for this problem) ideas or advice?

Nick1911 · « **Reply #1 on:** June 25, 2020, 12:10:58 AM »

I don't know the model, so can't help with known gremlins there.

Off the top of my head, 15.1V is rather high for a battery that was just at 8.3V to bounce back to. Check your measurement equipment. Car batteries normally only charge to 14.4V-ish.

Get a wiring diagram. The basic procedure is going to be to connect up the charged battery, pull fuses one at a time, and put a higher range current (10A) multi-meter in place of the fuse. Should be reading nil. You'll find one that's pulling power. See where that goes on the wiring diagram, and start chasing it.

zxcvbob · « **Reply #2 on:** June 25, 2020, 10:17:02 AM »

A common one with Chevy pickups is the under-the-hood convenience light staying on when you close the hood. Don't know if Subarus have those or not.

sumpnz · « **Reply #3 on:** June 25, 2020, 10:18:29 AM »

No light under the hood.

230RN · « **Reply #4 on:** June 25, 2020, 10:45:02 AM »

Had truck battery regularly die in two days of non use.

Pulled + on battery, hooked in an ammeter.

Showed regular on and off drain with about a 20 second-ish cycle.

Tracked it down to cigarette lighter being pushed in just enough to make a lousy contact, warm up a little, break contact, cool down, make contact, etcetera, without actually popping the lighter out.

Reason? Son would put his feet up on the dash, apparently pushed in the lighter "just so."

On my Subie, I have to make sure the light by the tailgate is actually off. It's hard to see from the driver's seat, especially in daytime, after you've unloaded the car the night before and not realized you left that light on, and it kills the battery.

Also, make sure nothing's plugged into the cigarette lighter in the back.

Brad Johnson · « **Reply #5 on:** June 25, 2020, 10:53:50 AM »

Quote from: Nick1911 on June 25, 2020, 12:10:58 AM

I don't know the model, so can't help with known gremlins there.

Off the top of my head, 15.1V is rather high for a battery that was just at 8.3V to bounce back to. Check your measurement equipment. Car batteries normally only charge to 14.4V-ish.

Get a wiring diagram. The basic procedure is going to be to connect up the charged battery, pull fuses one at a time, and put a higher range current (10A) multi-meter in place of the fuse. Should be reading nil. You'll find one that's pulling power. See where that goes on the wiring diagram, and start chasing it.

15.1v is essentially impossible. Lead-acid cells produce 2.1-2.2v per cell. A 12v car battery with its six cells is capable of producing no more than 13.2v with a full charge on a perfect day. With the car running, you should see 13.8-14.5 volts at fast idle. Any more and you have a faulty voltage regulator. Any less and you have a faulty alternator.

Use Nick's suggestion about bridging the battery connection with an amp meter and pulling fuses one at a time. It's old school and takes time, but it works. You should see 30-50ma in a Key Off situation (presuming no underhood lights or other accessories in operation). Once you've identified the offending circuit you can begin sequentially checking all the modules on that circuit.

Brad

230RN · « **Reply #6 on:** June 25, 2020, 11:05:21 AM »

By the way, batteries do recover all by themselves due to repolarization over a little time. That doesn't mean they're up to full capacity --straight no-load voltage doesn't usually tell you a whole lot. That's why they sell hydrometers to test electrolyte density in older batteries and battery shops put on a heavy load for testing.

However, there are tables for voltage / temperature / state of charge. available.

One of many examples:
https://www.scubaengineer.com/documents/lead_acid_battery_charging_graphs.pdf

K Frame · « **Reply #7 on:** June 25, 2020, 11:56:01 AM »

At this point could literally be anything, I would think. The only way to really figure it out is to chase the particular circuit that's got the load on it, as has been suggested.

Jim147 · « **Reply #8 on:** June 25, 2020, 11:57:28 AM »

How many days did it sit? My truck can only sit a couple days and it hard to start or have to jump it

sumpnz · « **Reply #9 on:** June 25, 2020, 12:02:58 PM »

New battery went in last Friday, and I tried driving it yesterday. So 5 days. Shouldn't ever be a problem to start a car after 5 days. 5 months, sure, I can totally see that.

Trickle charger and good ammeter coming today. As mentioned I plan to do the pull one fuse at a time method for a parasite load test once the battery is fully charged.

Nick1911 · « **Reply #10 on:** June 25, 2020, 12:11:51 PM »

Quote from: Jim147 on June 25, 2020, 11:57:28 AM

How many days did it sit? My truck can only sit a couple days and it hard to start or have to jump it

Helped a friend troubleshoot an issue like that with a GM truck. Turned out to the the instrument cluster, which was erroneously always on. We didn't care to pull the cluster and attempt to repair it, so we just bodged a relay on that circuit to only enable it in key-on.

230RN · « **Reply #11 on:** June 25, 2020, 03:30:17 PM »

Subaru? Don't forget to check that cigarette lighter in the left rear luggage area.

sumpnz · « **Reply #12 on:** June 25, 2020, 04:24:13 PM »

So, trickle charger wasn't recognizing the battery. Going to go to the auto parts store and get it tested. With the warranty it should be replaced if it's gone bad. Better multi-meter was saying 5.something volts.

Went ahead and pulled the alternator as it's right on top of the engine. I'll get that tested too. Belt needs replacing anyway.

If the battery is good I'll have them charge it. If not I'll get a replacement. If alternator is bad I'll buy one from the auto parts store if it's kinda close to the Rock Auto price. Otherwise I'll get it from Rock Auto. If the alternator is still good I'll just get the replacement belt locally.

Once all that is done I'll move onto the parasite load test.

K Frame · « **Reply #13 on:** June 25, 2020, 05:39:33 PM »

OK, so if the new battery went in last week... did you drive it at all after that but before you tried to start it today?

If you didn't, I can't see how it would be the alternator, since the alternator only does its thing when the engine is running...

I suppose a voltage regulator could problem could allow current to be drawn back from the battery, but man, that's a stretch...

sumpnz · « **Reply #14 on:** June 25, 2020, 06:10:36 PM »

Nope, no driving since it was put in. Only thing the alternator might have done is developed a short that drained the battery. But, it's an easy part to pull and test. And the belt needs replacing, so might as well do that.

Jim147 · « **Reply #15 on:** June 25, 2020, 09:43:39 PM »

A diode in the voltage regulator can do that.

Nick1911 · « **Reply #16 on:** June 26, 2020, 01:02:08 AM »

Quote from: Jim147 on June 25, 2020, 09:43:39 PM

A diode in the voltage regulator can do that.

I've seen this too. And heck, it's free and you already pulled the part, see what the autoparts place has to say.

Was your 5-volt reading with the battery still connected to the car, or had you left it disconnected from the other day?

sumpnz · « **Reply #17 on:** June 26, 2020, 01:04:27 AM »

Disconnected from the other day.

Nick1911 · « **Reply #18 on:** June 26, 2020, 01:11:43 AM »

Quote from: sumpnz on June 26, 2020, 01:04:27 AM

Disconnected from the other day.

Hmmmm.

I'll be interested to see how the test goes.

sumpnz · « **Reply #19 on:** July 02, 2020, 12:32:28 AM »

SWMBO took the battery and alternator in. Battery was fried. Alternator was fine.

So, either infant mortality on the battery or there's something on the car that killed it.

I'm a little reluctant to hook up the new battery until I can figure out what might be causing the problem. Don't want to kill another brand new battery.

Ideas?

Hawkmoon · « **Reply #20 on:** July 02, 2020, 02:09:06 AM »

Are the any junkyards or parts houses near you that sell used batteries? Around here I can usually find something for $15 to $25. I wouldn't choose that for my daily driver, but it might be worth it as a test mule. They usually have a 90-day warranty. If you kill it, being used they probably won't quibble about replacing it.

cordex · « **Reply #21 on:** July 02, 2020, 05:53:54 AM »

Was your battery not covered by warranty?

Brad Johnson · « **Reply #22 on:** July 02, 2020, 09:21:56 AM »

Check for KOEO draw. Regular car batteries sulfate if depleted more than 15-20%. Sometimes all it takes is once to be unrecoverable.

Brad

sumpnz · « **Reply #23 on:** July 02, 2020, 10:07:38 AM »

Battery was replaced under warranty, but they said it won't be again if it's the car killing it.

I'll look for a used battery. Might pull the one from the dead Camry in the driveway if nothing else, though I'd probably want to put that on a charger before using it to test the Subaru.

Jim147 · « **Reply #24 on:** July 02, 2020, 11:28:23 AM »

I would think for the car to kill it that bad in five days it would look like an tig arc when you tried to hook the second cable up.

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Author Topic: Electrical car issue (Read 2022 times)