Isolating flat battery cause (CAR)

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Batman

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#105922 14-Jul-2012 10:02

I just got a car delivered - journey was about 350km and took around 36 hrs by company.

When I picked up the car it had a flat battery and I noticed the car door sensor is active (all doors are shut but the red light was on). No stereo was on, no lights inc boot light was on.

Could this be the cause or do you think someone left the lights/radio on during transit?

If I want to get rid of the light is there a simple fuse I can unplug?

Either way it's going to a mechanic for full service but just worried about the weekend - although I have AA subs PHEW

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#655381 14-Jul-2012 10:31

Use a multimeter. Measure the idle current when the car is off, which means you need to put the meter in between the battery terminal and the battery lead. Either pos or neg terminal is fine.

Make sure you have a multimeter capable of measuring 10 amps, and *do not* try to start the car with the multimeter in place.

The idle current should be very low, in the order of 10s of mA. if it's not, then there's something wired wrong.

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#655385 14-Jul-2012 10:45

OK!

you mean put the meter on positive and negative terminal of the battery? (sorry i'm so dumb)

mjb

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#655389 14-Jul-2012 10:57

joker97: OK!

you mean put the meter on positive and negative terminal of the battery? (sorry i'm so dumb)

Good grief no... that'll make a nice loud bang, possibly welding your multimeter leads to the battery terminals, and destroying the meter ;) (plus also increasing the risk of a very nasty battery explosion - take extreme care!)

No, I mean between the battery terminal, and the terminal clamp - so you have to remove the lead from the battery, and put the multimeter in series, effectively reconnecting the terminal and clamp via the meter

Wear safety glasses when you do this. (as you should around all batteries over an amp hour, but especially lead acid)

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#655390 14-Jul-2012 11:00

joker97: OK! you mean put the meter on positive and negative terminal of the battery? (sorry i'm so dumb)

Definitely not - That will destroy your meter!!! (or at the very least blow your meter's internal safety fuse).

If you are taking it to an auto electrician on Monday, then just wait. You probably won't need to call the AA anyway if you start with a fully charged battery, but it is good you have the AA as backup.

Removing a car fuse will give you peace of mind but it will probably remove power from all dash lights and likely the backlighting for the speedo at night as well.

If you want to go that way then consider naming the make and model and the names of the cabin fuses you have to choose from. My advice is just wait.

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#655393 14-Jul-2012 11:03

gzt: If you are taking it to an auto electrician on Monday, then just wait.

To be honest, I'd agree. It could also be that the light that's on is also used as a fault indicator, or a "voltage too low" indicator? What's the car?

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#655419 14-Jul-2012 11:42

Doubt very much the door open light is used as a fault light.
Sounds like door not shut correctly and interior light drained a worn battery.
Get battery charged and checked.

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#655449 14-Jul-2012 11:57

ah got it. in series not in parallel ... kind of ...

it's a subaru impreza the previous body (2001) and has a uniden alarm ... googling seems to suggest it could be the alarm or it could be some other issue

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#655514 14-Jul-2012 13:07

Googling car electrical issues won't help unless you know a bit about cars. It's like googling medical issues, my colds always seem to be Ebola or bird flu! Lol

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#655530 14-Jul-2012 13:44

TheUngeek: Googling car electrical issues won't help unless you know a bit about cars. It's like googling medical issues, my colds always seem to be Ebola or bird flu! Lol

LOL how true !!!

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#655531 14-Jul-2012 13:45

ok -

will this LIGHT cause my battery to drain?

will the alarm be "waiting" for the door to close causing battery drain?

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#655535 14-Jul-2012 13:49

Was the interior light set to "door"?

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#655537 14-Jul-2012 13:55

need to know how flat the battery was and for how long but given the distance it should be fully charged by now but need to have it checked. The car is 2001 so is most likely on at least 2nd battery if not 3rd so check for a date stamp on battery. Here in NZ you usually get a letter representing month first (A=Jan, B+ Feb etc) second should be a number representing year as in 5=2005. Most batteries these days designed for about 3 - 4 years normal use but if it has other extra's fitted it may shorten life.

If its a non factory fitted alarm and not well done it could well drain battery but would need to be sitting for a few days and battery not at full charge.

Your car is post 2000 but may have an alternator that is max 14.4 volts and is you have a lead calcium battery it needs 14.8-ish to recharge if flattened off meaning it won't charge but if its not getting excessive drainage you would never notice it but something else to get sparky to check.

As has been said if its starting ok cold then wait till Monday.

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#656909 17-Jul-2012 10:29

If the battery was _completely_ flat, as in the dash lights would barely light, then you might want to get the battery tested properly. Lead-acid's don't like being completely flat for very long.

AGM (Absorbant Glass Mat) batteries seem to be the new thing, less problematic than traditional Lead-Acids and have less charge-leakage.

Leaving the stereo on will kill the battery, the "door open" lights shouldn't unless it's over a few weeks.

@KnightNZ

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#656916 17-Jul-2012 10:44

With all the can bus stuff in the cars these days they can be powered up but not actually doing anything and chewing thru the power. With integrated unlocks and alarms it is very possible to end up with it constantly awake because of a fault.

Add to that the butcher job that most "alarm installers" do on cars there is plenty of scope to stuff up and leave something running.

Richard rich.ms

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#656940 17-Jul-2012 11:26

If I leave the overhead lights in my car on the battery's flat in the morning... at least it was with my old battery.

I suggest you charge it up, use the car, and if you have problems have the AA or a garage test the battery to see if it needs to be replaced. If not it means there's drain, so take it to an auto electrician to diagnose.

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