Having a few flat battery problems!

[pugface406lx]

Hello ...i have my 406HDI 2.0 (110) In dock again and cant seem to bottom out the problem with the battery going flat after a few days of standing!
I have no battery charge light on so assume the regulator is ok.....I charged it right up over 24hrs as Halfords said to do because i took the battery back to them thinking it was a duff cell...they said no its fine its holding 12v.
Not sure where to look now as it starts and runs fine then when its left a few days like recently...i went to get in...no joy with the remote C/L so opened it on the doorlock and put key in ignition.....absolutely nothing on the dash or clocks.....not a bulb lighting up at all....it was as if there was no battery on the car. I swapped the battery with another one of my other car and she fired up no problem.
Not really sure where to look now......any ideas anyone?

regards
pugface

[steve_earwig]

That sounds like something is staying on and draining the battery. I'd start by checking anything that's not standard on the car (aftermarket stereo, amp etc.), failing that reading what the drain is on the battery with everything turned off.

[Busman]

As Steve says it does sound like something is staying on draining the battery. One that happened to me years ago that gave the same symptoms was the boot light staying on sometimes due to a dodgy switch. Also I would imediatley suspect anything that someone has been messing with such as radio or after market security systems.

[pugface406lx]

Hi again thanks for that guys...I have recently had to have the ecu sorted as I had a problem there...the people who fix them told me they had disabled the immobiliser as this causes problems with starting alot on the 406. Now i get a warning note on the dash each time i go to start saying 'Electronic Ignition Fault' and the icon on the speedo clocks showing a door key in a box...but they goes off as soon as it starts up which seemed to be fine.

I checked the boot light...(mines an estate model) and that seems to go off when boot closed (however doesnt always come on when opening boot sometimes delays until after boot is up)
If it was alternator problem would I notice anything on the dash like battery light? this goes off as normal as soon as she fires up.

Switched both courtesy lights in cabin off but still having same problem.....could it be a dodgy fuse maybe? how would i tell?

pugface

[Malc]

Check the following voltages across the battery terminals with an accurate digital voltmeter..
a) Car running and alternator charging battery 14.4V
b) Switch car ignition off and check voltage with positive terminal removed... 12V +
c) Check voltage with positive terminal in place.
If there is any difference....
a) not over 14V your alternator is naffed.
If there is a substantial voltage difference between b) and c) it shows you have something on board that is discharging the battery when the car is not running.

Hope that helps.

[pugface406lx]

Thanks malc I will check that out.

pugface

[Malc]

Cheap digital multimeters are available and almost chuckaway if anything goes wrong. Mine cost me euros 6 in my local diy and the same must go for GB..
If there is some small permanent discharge it may not be noticeable on a voltage check and will only show up on a current check.
Do you know how to do this?
I'll be working on my 406 this coming week and will give you some figures for comparison..

[jasper5]

If you suspect the alternator is causing the battery drain disconnect the wires at the alternator and see if the battery holds charge or not.

[Malc]

A word of warning against disconnecting wires if there is an unknown drain on the battery while the ignition switch is in the off position!
This could result in an electric spark which can instantaneously kill anything solid state in it's path and that could be... alternator diodes, blower motor voltage control unit, bsi, ecu etc etc..

[jasper5]

A word of warning against disconnecting wires if there is an unknown drain on the battery while the ignition switch is in the off position!
This could result in an electric spark which can instantaneously kill anything solid state in it's path and that could be... alternator diodes, blower motor voltage control unit, bsi, ecu etc etc..

Wouldn't you disconnect the battery first?

[Malc]

Wasn't sure what your original post was trying to prove.
Disconnect wires at alternator and now disconnect battery?
Or disconnect battery then disconnect alternator wires?
Then what?

[steve_earwig]

Wouldn't you disconnect the battery first?

I thought that was what you meant Malc - if there's still a load somewhere on the battery there'll be sparks as he disconnects the battery, with high voltage spikes that could damage stuff.

b) Switch car ignition off and check voltage with positive terminal removed... 12V +

There's meant to be a gap of a few minutes between turning the engine off and disconnecting the battery (driver's window open, everything off, left trouser leg rolled up...)

Personally, I have one of these to stick across the terminals when I'm disconnecting/reconnecting the battery: http://www.thetoolbar.net/contents/en-uk/p98.html

[Malc]

Wouldn't you disconnect the battery first?

I thought that was what you meant Malc

Thought that is what I meant where Steve?
I was only commenting there are relevant voltages under normal circumstance between battery off/on load (with ignition switch off), alternator charging etc and can only be found out by using a digital voltmeter which is much more accurate than an old fashioned moving coil multimeter.

[jasper5]

Wasn't sure what your original post was trying to prove.
Disconnect wires at alternator and now disconnect battery?
Or disconnect battery then disconnect alternator wires?
Then what?

Well, you were warning about causing problems by disconnecting wires, I was noting that it is best to disconnect the battery if disconnecting wires....yes, connect the battery up again after you have disconnected the alternator wires and isolated them.....then see if the battery gives the draining fault....if all is well afterwards then the alternator is the problem, if not, then you look elsewhere.

Process of elimination!

[Malc]

Whatever turns you on...
The alternator charging voltage at 14 plus volts is good enough for me without the necessity to disconnect any wires.
Just fitted a fully charged battery for a long trip.
Car running... Alternator charging voltage 14.36V..
Car ignition off... Battery disconnected 12.88V....Battery connected 12.85V...
The 0.03V difference due to normal permanently switched on electronic circuit drain.
My guess if there was any other erroneous drain the 0.03V difference would be a lot higher.