Any one know about cage electrics?

[Mully]

Hi all,

We currently have Miss Mully's mother's car at our house. Part of my brief was to get it WOFd and Regod and running properly.

Mainly done, including a new battery. Here's where it gets weird.

It was a brand new battery
Started the car and drove around last weekend
Went to start last night, and the battery was flat (no central locking, not even clicking from the starter motor). This is 5 days after it was last used.
What I want to know is: Is there a way to tell if there is a draw on the battery while it is sitting. As far as I know, there is only the clock on the radio which should be drawing power.

Thanks in advance.
Mully.

[marty]

stereo clock should be internal battery.

check the boot light is not turned on/not switching off when boot closed.

put a multimeter across the battery when switched off to see if anything is being drawn.

in a very quiet/dark garage disconnect the battery, then reconnect it, with the key off and doors all closed. listen/watch carefully for relays clicking/lights coming on. there should be no spark jump in this state.

[Dan Mapp]

Disconect the earth on the battery and put a amp meter between the lead and the termanal shouldnt be drawing more that .2 of a amp. ps make sure everything is tured off or you get a fulse reading and dont try to start car.

[CookMySock]

Disconect the earth on the battery and put a amp meter between the lead and the termanal shouldnt be drawing more that .2 of a amp. ps make sure everything is tured off or you get a fulse reading and dont try to start car.If you dont have an amp meter, put a tail light bulb or similar in between the battery and the disconnected battery terminal, and measure the voltage across the bulb terminals, and then post here that voltage and the wattage of the bulb.


Steve

[Mully]

Thanks lads. Will make a start on that tonight.

Forgot to mention, although it hasn't come up, that I took it to a "Free battery/alternator" check place and they said the alternator was charging fine.

Any more ideas, please keep them coming.

[marty]

Disconect the earth on the battery and put a amp meter between the lead and the termanal shouldnt be drawing more that .2 of a amp. ps make sure everything is tured off or you get a fulse reading and dont try to start car.


that was what i meant to say - checking across the top of the battery in Volts will only show if the battery is discharging - not by how much

[davereid]

DBs idea is good.

What it sounds like is that you have something drawing current all the time.

This is pretty standard on many cars by the way, the electrics don't normally shut down entirely, they just go onto standby.

Some cars are so bad they are hard to start after only a week or ten days.

To locate the circuit in question you need :

An amp meter, or a voltmeter and a bulb to do DBs trick. (I'll assume you have an amp meter).

Get the amp meter, switched to DC amps or DC milli-amps range.

Put the amp-meter POS on the battery NEG.
Put the amp meter NEG onto a good earth.

Disconnect the battery earth lead. The idea here is to let the amp-meter carry the current that the battery earth lead was carrying.

If you do it carefully, you wont lose power to the cars electrics at all. This is a good idea, as radios may need resetting, electronic ECUs and tranmissions may need to "re-learn" therir settings etc.

The amp meter will tell you how much current the car is drawing with everything off.

Anything above 0.1 - 0.2 amps will require further investigation. Watch the amp-meter as you remove fuses. It will drop when you pull the fuse on the circuit that has the excessive load. Try non-essential fuses first.

Another tip - wind the driver window down before you start. Central locking systems will often lock the car on yu if they get a spike.

Good luck !

[Mully]

Alright gentlemen, update.

Have jumped the car and run around for half an hour to make sure all charged. Seems to be charging at about 14 volts when running.

Whipped the negative terminal off and did as Dave suggested.

With the Voltmeter set to "DCA" (which, I presume is DC Amps), the only reading I get is "-1". This doesn't change when we pull any/all of the fuses.

What am I doing wrong??

Thanks,
Mully

[davereid]

The meter is not reading anything - check that you dont have to move one of the leads on the meter to an "amps" socket. It sounds like the meter is connected incorrectly... pm me if you need to be walked through it..

[Ryder]

could be a failing alternator which isnt providing a charge to the battery. if the batery is weak enough a clock light could be enough to run the battery flat overnight.

might even be a bad earth.

could also be a dud battery....???

that would be my first few guesses. i hope you do figure it out...best of luck with it :niceone:

[Ryder]

Alright gentlemen, update.

Have jumped the car and run around for half an hour to make sure all charged. Seems to be charging at about 14 volts when running.

Whipped the negative terminal off and did as Dave suggested.

With the Voltmeter set to "DCA" (which, I presume is DC Amps), the only reading I get is "-1". This doesn't change when we pull any/all of the fuses.

What am I doing wrong??

Thanks,
Mully


while doing the above...with the engine running...does the 14 volts change when you flick the headlights on and off?

[Mully]

The meter is not reading anything - check that you dont have to move one of the leads on the meter to an "amps" socket. It sounds like the meter is connected incorrectly... pm me if you need to be walked through it..

Cheers Dave, you could very well be right. I'll fire you a PM later. We did find a wire simply attached to the fusebox (i.e. a botch job, no fuse or anything).


could be a failing alternator which isnt providing a charge to the battery. if the batery is weak enough a clock light could be enough to run the battery flat overnight.

might even be a bad earth.

could also be a dud battery....???


Nope. Alternator and battery have been checked (new battery as well)


while doing the above...with the engine running...does the 14 volts change when you flick the headlights on and off?

Dunno. Good question. Something to look at, anyway.

[Motu]

Nope. Alternator and battery have been checked (new battery as well)


You have just made a mistake.

Check,recheck....double check your recheck.

I very much doubt there is a drain - the alt will be low on output dragging the battery down.

[FJRider]

Remove the terminal leads and clean battery and connections with hot water/baking soda mix and RE-connect. Charge may not be getting past the terminals...

[Mully]

I took it to an Auto-sparky place that does free battery and alternator checks. He plugged his machine into it, and said the alternator was fine and the battery was holding charge.

Yesterday (when all my troubles seemed so far away), while the car was running, the battery was registering 14-odd volts. Once the car was off, it was registering 12-odd volts. I would have thought that was pretty much where it needed to be.

I understand there will be a slight drain on the battery, but to die completely (no central locking, no clicking from starter motor etc) inside 5 days seems bizarre to me.

Dave, I'll PM you when I have the volt meter in front of me, so I can tell you what exactly it was switched to.

[Motu]

My daughter has a similar problem with her car - battery going flat for ''no reason at all''.She had the battery and alt output checked at my old shop,and was told they were both fine.I just check not 20 minutes ago - and the alt output is low.It is charging,but not quite enough.I have very seldom seen discharges draining batteries,it does happen,but not often - but altenators,startors and battries drag each other down...one is the culprit,putting load on another causing that one to crap out.

[Mully]

Thanks Motu. What should it be charging at? I would have thought 14-odd volts was more than enough?

Thanks,

[Motu]

Odd volts are not enough,more accuracy is required in electrical work.You need to check it under load,how quickly it cuts back,and what it cuts back to.Check starter draw as well - starting,charging and battery are all closely related,if one is below standard it will drag the other down....and out.

[Ixion]

..
Yesterday (when all my troubles seemed so far away), while the car was running, the battery was registering 14-odd volts. Once the car was off, it was registering 12-odd volts. I would have thought that was pretty much where it needed to be.

...

If the battery is only 12 volts with engine not running, it is defective or the charging circuit is defective. It should be at least 12.8V.

12V, it only needs to loose half a volt or so and starting may be problematic. My BMW will not start reliably if the battery is 11.5V.

One thought though. Do you have a boot light that turns on automatically when you open the boot? If so, check the switch is not stuck. I have known them to stick on, leaving the light on all the time (usually they are not wired through the ignition key). Of course, since no one can see in the boot with the lid shut, no one ever realises the light is on when it should be off.

[ynot slow]

Or the light in glovebox can stay on.

[Chooky]

Yea the boot light can stay on without no body knowing,that'll suck the battery down........Had a toymotor that did that once ...
Pull the bulb out and chuck it away...ya dont need a boot light anyway..:cool:

[Mully]

No Boot light.
No glovebox light.
Pulled the interior light (wasn't working anyway)
(it's a 1990 Mitsi Lancer).

[racerhead]

There is also a possibility that the alternator is faulty and dis-charging the battery when the engine is not running. The way to check this is with a current draw test which has already being described, using a multimeter set to dc amps.
When the meter is connected observe the reading-if its above .5amps theres a problem
To be sure its the alternator you will have to disconnect the main positive on the alternator and repeat the test, you should now have a reading below .5amps
If the reading is still above .5amps the next thing to check would be all internal electrics and the easiest way to do this is just pull fuses out one at a time checking the meter readings after every fuse. If you pull a fuse and get a reading under.5amps this is the item that is causing the current draw.

[BMWST?]

and you will need to charge the battery properly too now...1/2 hr running around aint enough....you may manage, but the battery wont like it and you will shorten its life...beg /borrow/buy a charger