Looking for a sticking-plaster for the eternal battery drain

[oldie]

To circumvent an unidentified battery drain on my v6 Contemporary I bought an isolator. This has proved to be most effective in preventing flat-battery-dom. However the v6 has the battery in an easily accessible engine-bay location. Having already enjoyed an anticipated dead battery in my very newly acquired v8 I wonder if there is a way of incorporating an isolator. Attached to the battery would not pose an insurmountable problem, merely inconvenient and physically taxing. Could an isolating switch be put on the power supply line somewhere more readily available? What is the red wire running to the engine-bay fuse box? Is that the primary distribution point or does the wiring separate into different circuits elsewhere. If the v8 electrical drain is from one of the circuits running out of the passenger footwell fuse box is there a single supply wire that could be isolated? No prizes for noticing I am no automobile electrician.

[David]

Unplugging the boot mounted CD-drive and TV tuner MAY be the only sticking plaster you need for now, then you can maybe home in on the drain?

David

[oldie]

Hi David, I was thinking more generically. A persistent battery drain seems to be an oft commented feature of the v8.

My newly acquired beastie has been treated to a new battery today. However I fully expect a problem tomorrow morning. As mentioned in an earlier post the light switch module is permanently illuminated. Hopefully I'll get a replacement tomorrow in case it's the switch and not the supply to same.

[SCP440]

I have seen one of these used on a Jensen http://www.batterybrain.co.uk/produc...te-anti-theft/

Seemed a well made piece of kit and all you need to do is blip to switch it on and off.

Steve

[Nich]

It would be worth checking some of the known solutions first before embarking on the more drastic route of an isolator which as you rightly say is a 'sticking plaster' and will not solve the problems but just shelve them.
The problems caused by 'old' batteries are very strange, low battery voltage can cause problems with the wipers, the windows and the lights. Replacing the battery will at least give you a good starting point to work from.
Resetting the system by disconnecting the battery for at least 30 minutes should return everything to a normalised state and occasionally a few runs will reset the BCU if that throws up oddities.
The electrics under the floor of the boot can be affected by water ingress and may lead to systems not shutting down but this is an easy check, unlock the car with the key fob, open the boot to get sight of the satnav drive and wait for the light on the front of the unit to extinguish. This may take up to 10 minutes, whilst waiting listen for any sign of other electrical operation such as the fan on the TV tuner. Everything should stop...eventually. If it doesn't you have detected the source of your battery drain....if you have one. You can also check the voltage across the battery terminals with an ammeter but this requires a little bit more electrical knowledge.
It really is worth trying to identify the problem (that's if it isn't battery related).
You may well end up with an isolator but at least you will know what the problem is before going down that route.
If you are buying a battery make sure it's up to the job, information in the INDEX.
Nich.

[Nich]

If you are replacing the light switch module you may well have problems. As far as I know it carries information such as mileage covered and may well need coding to the car with a T4.

Nich.

[Ian]

Hopefully I'll get a replacement tomorrow in case it's the switch and not the supply to same.

Hi there, and welcome along!

Just a quick point about the LSM, if you change it, you'll get an error on the mileage display, some info HERE, there's plenty of help around to get one "virginised"

It's a good idea to get things sorted with a faulty LSM, they have been known to end up like this: https://www.flickr.com/photos/10615841@N07/10157740506/

Good luck!!

EDIT: Beaten to it! :-)

[oldie]

Thank you for the replies. By "light switch module" I mean the headlight switch to the right-hand side of the driver. namely this:
Would that need a t4? It's the immediate and obvious source of a drain as it is constantly illuminated.

The car doesn't have the high-line sat-nav installation.

The replacement battery is a Yuasa Silver HSB096 80Ah/760amps.

[simon227237]

Hi

Yes you will need a LSM matched to your mileage, I had the err on the dash caused by the previous owner swapping the LSM. I managed to get one matched from the 75and zt forum on a recon exchange basis.

I believe the LSM holds data including mileage and the vin number for the car, if the data doesn't match it shows the err on the trip mileage on the dash.


Simon

[WNJ516]

Just a query, can't the information from the old light module be transfered to the "New" module via T4 or "TOAF" software, did read on the 75 sight of one of the modules in the LSM being changed and it cured the problem, exactly same fault as Oldie's.