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Wierd electrical discharge - HELP

Jon_Tallis

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Jul 29, 2012
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wales
96 UK FZJ80. I'm losing charge overnight. 3.5A discharge between the positive battery post and the positive clamp.
I have the following connections to the positive side of my battery.
Main starter lead.
Two factory connections going to a box labelled "glow" - strange for a petrol
Aftermarket LPG system
Aftermarket towbar feed.

Here's the problem. Leakage down the main starter lead is 0, but I have an identical 3.7A leakage down each of the other circuits. The LPG and Towbar connections leak 3.7A even when their corresponding earths are disconnected from the battery.
I've pulled all the engine compartment fuses & Relays - discharge on all circuits remains the same.
How on earth do I start tracking this down?
 
So the wires are physically disconnected from eachother yet you're seeing the same current draw on all of them?!

Hmmm!!!!!
 
Look at this another way......
Is the item that's faulty finding an earth via either of those circuits...... trailer wiring could be sharing a common earth . Many times an item will find an earth or circuit path through other items....
I know this is on the + side of the circuit but same can apply.

Best way to try and isolate is to start pulling fuses and see what fuse causes the draw to stop....this might help isolate which circuit or item is faulty....

Disconnect the alternator multi plug and see what happens to your draw...I've known them to work perfectly but to cause a draw...
 
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I've pulled all the engine compartment fuses & Relays - discharge on all circuits remains the same.
Is there an inside fuse box on these, or is there just the one?

Doubly weird if you're seeing a draw and the circuit isn't fused, unless you've got a short circuit right near the battery end before the fuse box
 
Radio can also be another good one although not commonly that amount of draw.... the radio has a permanent live for the KAM as do possibly any other ECU's .....
Do you have a caravan type socket or normal 7 pin trailer socket ? the caravan type also has often a spilt charge relay and a permanent live
 
Disconnect the alternator multi plug and see what happens to your draw...I've known them to work perfectly but to cause a draw...


So common this one.

Also check any accessories that non standard, I note you say in your opening post ans you say 3.5 amps which increased to 3.7? FWIW a typical relay will not pull 3+ amps to become energised. It cannot be a dead short as @ 3+ amps that is close to being sufficient to melt wiring insulation.

EDIT: Just thought about this, the brake lights on an 80 work without the ignition on 2 x 21 = 42 watts divided by 12 volts is 3.5 amps.

Regards

Dave
 
Last edited:
Update on this.....
Update #1 - need to operate my multi-meter correctly - I had the probe plugged into the wrong port......lord knows what I was measuring but it wasn't amps! DOH!

Update #2 - have traced the discharge to 0.3 amp going down on of the original factory circuits but I can't trace it as the wiring colours don't correspond with the colours in my Max Elery manual. Is anyone able to post the factory wiring diagrams for a '96 UK spec FZJ80?
 
Thanks for the update Jon - easily done - at least it's starting to make more sense now!
 
Youre not alone in doing that Jon.
Isn't the Max Ellery manual u.s.a. ? Unlikely but would that explain different colour codes ?
No help to you whatsoever though !
 
0.3 amp makes much more sense..... still carry out the tests like disconnecting items and pulling fuses....
Anyone here in the UK got a similar vehicle that can measure what their draw is....?
 
Maybe worth doing a voltage drop test across each fuse to see if you can identify what's pulling the current. If you do it that way, you can avoid pulling fuses out.
 
Youre not alone in doing that Jon.
Isn't the Max Ellery manual u.s.a. ? Unlikely but would that explain different colour codes ?
No help to you whatsoever though !
Yes, that was my thought too (the USA bit, not the "no help whatsoever" bit
Maybe worth doing a voltage drop test across each fuse to see if you can identify what's pulling the current. If you do it that way, you can avoid pulling fuses out.
Sadly I'm only home on the weekends at the mo and had a whole 30mins to work on the 80 this weekend, so that's next weekend's job.
Hoping someone will post the wiring diagram by then......
 
Update on this.....
Update #1 - need to operate my multi-meter correctly - I had the probe plugged into the wrong port......lord knows what I was measuring but it wasn't amps! DOH!

Update #2 - have traced the discharge to 0.3 amp going down on of the original factory circuits but I can't trace it as the wiring colours don't correspond with the colours in my Max Elery manual. Is anyone able to post the factory wiring diagrams for a '96 UK spec FZJ80?
First if you had the test leads in the wrong locations you may have damaged the DMM internally, often when testing amperage anything over 10 amp will damage the internals unless it is fused? I would run a few tests, volts, resistance and so forth, or if there is damage then it may be enough to skew your results.

Try with the DMM on amps amps and the probes in the correct socket disconnect the negative cable from the negative terminal and put your probes between the two, conventional thinking is that power runs from positive through the load and back to the negative, but that is not strictly true, after many years it was found the.....jeez can't remember the correct terms, but current flows in the other direction. As all wiring maps have been standardised (is that spelling right?) to change them to show the true direction of current would cause worldwide confusion, it is not mentioned much because many don't quite get it anyway, you will get a better reading given the mass of the negative connection.

And secondly, if you adjust your wheel bearings as per the Max Ellery book you will destroy them in about ten minutes of driving, it is a known typo.

Also as per the note above about that being a USA publication might make sense if your wiring colours don't match?

Regards

Dave
 
Thanks Dave.
The DMM is fine, it's a Fluke meter (£££££) and pretty much unbreakable. Reading sensibly now the pilot error has been corrected
I'll try the negative post idea, I'd actually forgotten that from my electrical theory many years ago but it makes sense ..

Thanks for the heads up on the wheel bearings! I'll remember that, fortunately they're not on the list yet....
 
Obviously when your meter is hooked up in series don't start the engine or do anything that might draw more than 10A!

Clamp meters are best for measuring current draw on these because you dont have to disturb the wiring to try and get your meter in series
 
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