Thread: flat batteries - what's causing it ?

You are going to need a multimeter. After you get it going again and charge the batteries up, it will be time to see where the power goes when the ignition if off. Multimeters usually have a 10amp ammeter capability, so you can interrupt the power at the battery and work backwards. Some of the likely candidates are aftermarket accessories, interior fittings re-wired off the wrong circuit and the alternator windings drawing current. Of course check and clean the earth points and fittings of the twin batteries which should be in parallel with or without some sort of split charging system (Although I have twin batteries on my disco without anything fancy, and it's ok).

Since both batteries are brand new, the likelyhood of one of them draining the other is remote - but possible. You could always disconnect one of them for a week and see how the other copes.

I have an 88 Classic 3.9 retro fit with dual fuel, after market computer & later model instruments.

I think that this says it all.
The fault is MOST probably with one of these things.
I trust seeing you say you have no electrical ability that you did not fit either.
My guess it is something to do with the gas/petrol change over switch if the fuel gauge reads full with the ign off. maybe there is a relay that has stuck "on".
BUT if you have no diagniostic ability maybe its better to take it to an electrician.
Regards Philip A

my fuel gauge reads how much petrol is in it regardless of ign position, always has, unmodified, in a 94 classic.

Well my 92 doesn't.
Regards Philip A

my 90 & 93 models also don't .....

You don't have an ERPS?

My defender uses 200mah but the addition of the ERPS increases it by 200mah. That is enough to make all the difference.

You really need to get in there with an ammeter and see where these volts are going.

Just looking here and I also am thinking a relay on the fuel side may be the cause. Possibly a non resistor relay on a low load input that will stay on if there is any feed back on switching side. Does that gauge stay up on either petrol of gas? They are definitely not meant to in those old girls.

Tony

Thanks for the reply's.

I suspect a relay as well, particularly as this is a recent develovement - leading me to think that it might be a sticky contact of some sort.

only the petrol gauge shows as full - the LED's for the gas are not lit when the ignition is off.

& I have no idea what an ERPS is !