Another bloody bodge.

In my main build fred, but probably worth sticking a pic here:



Crap old wiring from alternator to starter motor on left, that ran round all 4 sides of the engine, and nice new one that simply goes from alternator, along intercooler pipe onto starter motor. Also made of wire actually rated to 100A, which is the output of the alternator. Old wires were warm to the touch when the engine was running...

Ok, problem still not fixed. Something is drawing a very small amount of power somewhere.

Car wouldn't start this morning, battery voltage was 11.76v. Stuck the old battery on which had been on charge for 18hrs, it had 12.79v available and started the 90 easily. Ran it for an hour or so whilst collecting a sofa, just got home, switched it off, put the meter across the terminals and it appears to be losing 0.01v every minute or so.

Bloody irritating now.

As trax suggested, get your multimeter in series with the battery and measure the amp draw. Don't start it or switch the glow plugs on with the meter is series. Note, that you normally have to plug the meter leads into different terminals to test in series, then pull your fuses one by one until you hopefully identify which circuit is at fault.

Have you recently added any new accessories?

Done it several times with 3 different multimeters. Each registers nothing when wired to the 10A socket on the meter. No electricals added at all - barring a USB cigarette lighter phone charger that was removed weeks ago, there is nothing aftermarket in the wiring. That said, who knows how many more bodges there are in the loom waiting to be discovered?

Have you checked the main earth from battery to gearbox? (As in- take it off and clean up connections) Wouldn't hurt to put a few more earths on (battery to chassis and chassis to engine or extend the gearbox earth to the engine near the starter motor)

To be honest, the earths are my next stop. There's already two I've found that are missing from the Disco engine, so I'm going to replace the main battery to starter positive cable, and all the main earth cables. Need to head back to Maplins for some black 4AWG.

sp00k said:

As trax suggested, get your multimeter in series with the battery and measure the amp draw. Don't start it or switch the glow plugs on with the meter is series. Note, that you normally have to plug the meter leads into different terminals to test in series, then pull your fuses one by one until you hopefully identify which circuit is at fault.

Have you recently added any new accessories?

Click to expand...

You could also confirm your meter is set up correctly be turning your sidelights on, that will give you a couple of amps draw so that you can prove you have things connected correctly.

Bustrucket said:

Ok, problem still not fixed. Something is drawing a very small amount of power somewhere.

Car wouldn't start this morning, battery voltage was 11.76v. Stuck the old battery on which had been on charge for 18hrs, it had 12.79v available and started the 90 easily. Ran it for an hour or so whilst collecting a sofa, just got home, switched it off, put the meter across the terminals and it appears to be losing 0.01v every minute or so.

Bloody irritating now.

Click to expand...

Battery voltage will always drop once you shut engine off, its just the battery stabilising itself after coming off charge, that said if something is draining your battery it will also cause a voltage drop - just don't expect it to stay at the voltage it was at when engine was running

Ok, finally had some time during daylight to investigate further. Set the multimeter to 200mA (wired in series from battery) and I'm getting a drop of 0.88. Removing the 1st fuse (R/H dipped beam) drops this to 0.86, but it drops no further even when all the fuses and relays are removed (including indicator flash module). Therefore it can only be escaping down an unfused wire - the only unfused wires i'm aware of are the main battery cable to the starter and alternator, and the twin brown wires from the starter that run through the bulkhead (presumably to the fusebox).

If you have got your meter correctly connected and the reading is 0.88ma (0.009 Amps) then that is fine, nothing to worry about. Did you try it on a higher range (10A) and try the sidelights to confirm everything was connected and working properly?

Yep. Turned sidelights on and meter gave a reading on the 10A setting (though for the life of me I can't remember what it was!). Problem is, somewhere, somehow, the battery is still losing charge if left connected. So far, a new alternator, battery and power cable have not solved nor altered the charge issue. I have ordered a battery master switch which I'll fit Monday, but it doesn't get rid of the problem.

Cheers for the help so far - it has been very useful

You could always try disconnecting battery negative terminal when you not using it, if it still goes flat you've got a duff battery

That is what I do every time I switch it off at the moment, hence fitting the master cut-off switch. Battery holds charge fine when its not connected to the car.

Cheers

Test between the positive and and earth, without anything connected to the battery. I once had a battery that self-leaked, apparently not uncommon.

Bustrucket said:

That is what I do every time I switch it off at the moment, hence fitting the master cut-off switch. Battery holds charge fine when its not connected to the car.

Cheers

Click to expand...

If that's the case then the current draw from the battery when switched off must be more than the 0.009 amps previously mentioned (at 0.009A that is about 1 amp/hour battery capacity used every 100 hours - a 70Ah battery would in theory last over 9 months!)