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Car Battery Checks OK, But Fails After 10 Days Parked

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January 01, 2019, 07:19 AM
NK402
Car Battery Checks OK, But Fails After 10 Days Parked
That's not a Subaru is it? Outbacks come with notoriously poor batteries. My salesman told me they replaced 17 of them under warranty last winter.
January 01, 2019, 07:43 AM
henryaz
 
A little kit like this dummy fuse set, plus your ammeter, makes it easy to pull and check fuses for a parasitic drain. When I had to check my wife's Sequoia to find the drain(s), I took and extra set of multimeter leads and cut off the probe end. Then installed 1/4" female connectors to it. Hook it up to a dummy fuse, just plug in and get an instant reading, them keep moving down the line. It turned out she had several parasitic drains, but the real problem turned out to be she was not closing the door or liftgate all the way. Roll Eyes


When in doubt, mumble
January 01, 2019, 10:11 AM
Perception
quote:
Originally posted by sns3guppy:
quote:
Originally posted by Perception:
My GTO has a parasitic draw that has gotten worse over time. It takes less than 24 hours to draw the battery down to where it will no longer start. I haven't been able to track it down yet, so every time I get out I disconnect the battery. It's a pain in the ass, but it keeps me from being stranded.


How old is the battery? A load that's attached to the battery shouldn't be increasing; a load is a load. Your battery conditions sounds more like it's deteriorating (do a load test, check specific gravity after a full charge), it's not getting an adequate charge (clean connections, check alternator function), or isn't serviced (check fluid level).

Any time a problem increases and gets worse, it's a sign of inadequate charge or a bad battery, progressively it's often both.

It's a wise idea to put a battery disconnect in place if there's a known draw on the battery when not in service. There are various versions. I have one on the truck that's just a switch; raise the handle to disconnect, put it back in place to restore the battery. Far better than removing the terminal connection at the battery each time.

Check your terminals and connections are clean and bright, and your negative ground is clean. If the battery is approaching two years, replace it. If it's been discharged several times, replace it.


Battery and charging system are both good. I'm about 99% sure the problem is in the BCM wiring. GTOs are known for chewing them up, and I've had weird electrical gremlins popping up. Sometimes the radio turns itself on after the car is parked a few hours, and the interior lights have gotten weird.

The disconnect is a fantastic idea, I'll probably buy one today.



"The people hate the lizards and the lizards rule the people."
"Odd," said Arthur, "I thought you said it was a democracy."
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"Oh yes," said Ford with a shrug, "of course."
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"Because if they didn't vote for a lizard, then the wrong lizard might get in."