Battery dead in 5 day

[adyw]

Last week the battery in the car was fine, today, dead as, alarm did not go off, no little led on the dash, nothing, tested the battery and only reads 8 volts. Before I go and get another battery is there something I should check before I kill another battery.

[steve-V8s]

Passenger foot well light is very easy to switch on accidentally and not obvious to see, also check that both door switches are activating correctly. If you have the internal lights set to “off all the time” and the door is not correctly closed (or the switch is not detecting that it is closed) the light relay will still be drawing current, this will drain the battery quite quickly.

[mrcosmos]

Hi.It is quite easy to check for battery drain with little electical experience.Remove the negative terminal from the battery,then connect a test lamp between the negative terminal and the negative battery post.If the bulb lights up with everything switched off you have a drain problem.If this happens i would recommend calling an auto spark.If you have knowledge next step is to remove a fuse at a time until the bulb goes out then check that circuit for fault,normally faulty component or a cable is short to battery positive or something just switched on.Hope this helps.Regards,Dave.

[philmccann]

Fantastic advice, Dave

Not got a problem at the mo', but M+ for the future.

Cheers

Phil

[RFC1]

surely you would need to somehow isolate things which are always drawing current such as alarm, immobiliser and clock before this method would work? Not to mention the interior light relay/central locking switches on sills which apparently draws current when doors are open. spose you could tape the switch "in" to simulate doors closed.

sandy

[JonathanT]

I presume you work to an expectation of always drawing (say) 100-200mA for the alarm and clock. You could then push in the sill button and see the difference?

[mrcosmos]

Hello again,battey drains should be as low as possible but normally 20 to 30 mA. The most accurate method is to connect digital meter between neg battery post and neg battery cable,switch on meter and select the 10A scale then doors shut,next thing arm the car with fob.Depending on type of alarm system give a couple of minutes to settle then check meter reading,idealy 0.020/0.030A.When i bought mine in 2004 a previous owner had connected the amp in the head unit to battery+ so he could work stereo with key out of ignition[not a good idea].All amps internal and external should be ignition+.Hope this helps.Regards,Dave.

Edited by mrcosmos on Tuesday 15th January 18:08

[adyw]

Right I have now tried the disconnection of the negative terminal and yes have an amps reading on the meter I have, The first thing that I thought of is I recently had to replace the fuel pump relay.
If I then remove the new relay from the plug the amps reading drops almost to zero.
If I am reading thevmeter correctly the original amps reading is 5amp and post relay disconnection is around 1.5 amp. However I am not 100% sure if it is reading amps or milly amps. What I do know once you connect the battery the meter goes up and down with the indicator lights as the alarm goes on.
The question is should the fuel pump relay have this sort of effect or have I got a broken one again.
I have checked pin 30 and 86 on both fuel and main relay plugs which should be 12v and 0v and are, So I don't think it is something to do with the main ignition.

Has anyone any ideas before I need to take it to a garage.

[Uncle Fester]

mrcosmos]When i bought mine in 2004 a previous owner had connected the amp in the head unit to battery+ so he could work stereo with key out of ignition[not a good idea said:

.All amps internal and external should be ignition+.Hope this helps.Regards,Dave.

Why is it a bad idea?
When Carl Baker was putting in my new alarm, I asked if my radio could be wired to an auxiliary position on the ignition switch.
When he said there wasn't one I asked if it could be permanent live.
He said that's ok provided I don't forget to turn it off.
So he wired it that way and it's never been a problem.
I could take the face off, but don't usually bother when it's garaged.
Now if there's something fundamental wrong with doing this, surely Carl wouldn't have done it, or at least advised against it.

[mrcosmos]

Hi Uncle Fester,not 100% sure what the current drain is on an amp,be interesting to do a comparison between the two.For instance if an interior light was staying on that would cause a leak of around 300mA.The amp i'm sure would cause a considerable drain[battery+ is only required to retain radio stations].If i am incorrect please let me know.Regards,Dave.

[Simpo Two]

Bah, for real battery drain try an S-Type Jaguar - mine can totally kill a fully charged battery in five hours!

[TheGriffalo]

Something somewhere tells me the fuel pump relay isn't a standard type as it can "drain the battery" Can't put my finger on what type of relay it should be but I'm almost certain it's the problem.

Also the Sherlock Holmes "eliminate the impossible and whatever remains, however improbable, must be the truth" school of diagnostics applies here




Bosch Part Number 0732014112

or or Land Rover part AFU2913L according to the Chimaera Pages :spit:

Edited by TheGriffalo on Sunday 20th January 14:22

[GreenV8S]

TheGriffalo said:

Something somewhere tells me the fuel pump relay isn't a standard type as it can "drain the battery" Can't put my finger on what type of relay it should be but I'm almost certain it's the problem.

The fuel pump relay is a dual pole relay that switches the fuel pump and lambda sensor heaters on together. It is the same size and shape as the more common changeover relay and if you fit one of those the fuel pump will work correctly but you will have the lambda sensor heaters switched on when the ignition is off and vice versa. You should use the correct metal cased Bosch relay. This Bosch relay also has a diode in series with the control circuit so that it can only be energised one way round, presumably to prevent it from being back-fed by the ECU.