The V8 Owners Forum -

Have a strange one here,

the battery has started to discharge itself over a period of a week,
started doing it last week, and done it again this week,
had battery tested and its fine,
once it has been jumpstarted its fine all weekend,
but as soon as i leave it for a week its near dead when i go to start it again.
the only thing thats been done is the fuel sender changed.

I'm probably in teaching granny to suck eggs mode but . . . tried disconnecting the battery and measuring the resistance across the battery leads with an ohm meter (ie the resistance of the car) with the ignition off, disconect the clock first... if you have had the petrol tank out then I'm afraid it is probably time to look for chaffed or trapped wires to the back of the car. Has it had a tow bar on the back at any time? just the standard trailer electrics feed normally has a non switched posotive feed in it, after the tow bar is removed it just sits there looking for something to short against when you work on the back of the car.
Good luck
Mike

yeah its been checked Mike, and it seems ok, i may get another meter and try again,
regarding the sender, the tank stays in situ as the sender fits into the side of the tank.

I had a 1972 Capri 1600GTXLR a number of years back and it had a clock that worked on a set of points that wound up a spring. (From memoty electrically driven every 5 mins)

The points corroded and would stick and draw current but not enough to fire the solenoid to wind the spring. When driving the vibration kept the clock running. From memory it was not on a fuse but had some sort of built in fuse in the unit - the small current never blew this!

Cleaned the points and no more problem.

After all that your's may not even have the same clock!

Ian

Could it be related to the new alarm that was fitted recently

i thought about it but that was months ago mate, and has been sat in the garage happily for upto 3weeks since fittment and fired ok.
its just past 2 weeks its been playing up.

thev8kid wrote: the battery has started to discharge itself over a period of a week,
started doing it last week, and done it again this week,
had battery tested and its fine,
once it has been jumpstarted its fine all weekend,
but as soon as i leave it for a week its near dead when i go to start it again.

Tony, Could it be excess parasitic drain going above the typical 20 to 120 milliamps drawn by, clock and radio memory etc? Try either of these two tests without engine running, under bonnet lights off and doors shut.

• Connect 12-volt bulb in series between the negative cable and negative battery terminal. If bulb glows brightly, remove fuses one-at-a-time (including your new alarm) until the offending electrical component is found.

• A better method is use a DC ammeter inserted as per bulb (above). Starting with highest scale, check if load is above 120 milliamps. Remove fuses as above to identify faulty component.

If the tests are OK and there it no excess parasitic drain then the battery may not be as good as you think. There is lots more here:

http://www.vintagemodelairplane.com/pag ... ery01.html

any certain wattage bulb?
as will try this tomorrow too.

Fairly low wattage, lets say its an interior bulb or similar item draining the battery with say 5 watts = 1/2 amp then a 5 watt bulb in the test would just glow with half the voltage. A big bulb like 21 watts = 2 amps would probably not work. The ammeter test is more definitive.

Had a similar thing in a car a few years back. It was simply the battery slowly dying, It would hold a charge OK if the car was used every few days but any longer than that and the voltage would slowly drop below the limit sufficient to kick the engine over fast enough.
Got a new battery then checked all electrics and they were fine.
Just a battery dying.

seems to be just that,
a battery dying,
replaced it last friday (warranty thank god for 3yr ones) used all weekend,
went round tonite and turned over fine and fired up.