Electrical Problem

Sorry about the length of this post...

In the summer I posted about an electrical problem. Sterling advice from various MSC folk and a new alternator and battery later, the car ran fine :grinning: BUT... ever since then I've had to disconnect the battery every night to stop it from draining. :doh: I understand from an AA guy that I had to call out the first time it happened (car not starting) that the problem could be the diode pack on the alternator being duff, hence letting charge back out when the engine is off.

I duly changed the alternator again, and it's no different - the battery still drains when left connected. Both alternators that have been put on have been second hand.

I was thinking I would either try to get a new diode pack and brush assembly (anyone know who might do this?) or a brand new / reconditioned alternator.

HOWEVER... the other day I was sitting in the car with the ignition fully off and talking on my mobile and noticed the door speaker was making that noise you sometimes get from TVs, Hi-fis etc when a phone is being used nearby. There's no constant 12v on my car so I thought there should be no power to the speaker to enable it to do this... hence I thought the problem with the battery draining might be due to power being supplied to the HU / speaker all the time. When I came to think about it, the electrical gremlins (originally the alternator and battery packed up when I drove through an extremely heavy rainstorm) all started just after I wired in the HU.

If anyone could hazard any guesses as to whether it might be the first thing (diode pack) or the second (amateurish HU wiring), or option C that I haven't thought of, that's causing the battery to drain, I'd be really grateful.

On a different, but related, topic, the new battery I have has really small (about 7mm at the top) posts. I can't find matching terminals anywhere and have had to resort to using a bolt to take up the slack in a standard one. Does anyone know anywhere that might supply smaller terminals?

Cheers folks...


Grease Monkey!
A local motorfactors should be able to get them, either that or a nissan dealer (shouldnt be expensive) mine has the small pole battery as standard though so i thought all K10 micras had.

And on the power drain..... i would doulbe check the wireing and there should be 1 perminant live to keep the memory on the hardunit.
I think you've found the clue you've been looking for here!!

HU....is this an audio power amplifier for your music setup?

the only way you could possibly hear this (blipidip..bib blip dibit) sound is if your amplifier is permenamtly powered....you must have a permenant live connected into your amplifier.

I would forget the diode pack for now (personnaly)

Check that youre permenant and switched live connections to your amp are going to the correct terminals.....also check if there is an input to your amp that is used to switch it in and out of 'standby' and make sure it is switching properly with you ignition/accessories barrel (or the power button of any remote audio kit that may be wired to it).

There is also a chance that the amp is faulty and is permenantly on..

But I will put beers on it that if you disconnect your amplfier alltogether tou will not lose charge....
Thanks for your advice chaps.

HU....is this an audio power amplifier for your music setup?

No, I've just got a radio/cassette and a single door speaker at the mo. Reckon what I'll do is cut off all of the HU wiring and insulate the wires off, at least then I'll know for definite and it wouldn't take much to re-do it - seems like it needs re-doing anyway. Will see what happens.

Would be good to get this sorted - has been really annoying, and it's stopped me doing stuff like central locking - not much point if you have to unlock the car and connect the battery to get power to the system!! fwn

Thanks for the advice on terminals stonesie, will ring a few local places.

Thanks again guys

Fiji Nissan

Don't know much about auto electrical but learnt from my brother in law that if you are losing battery power (charge does not hold) then the best way to confirm power leakage is by switching off all electrical items such as light, radios, etc. Then undo the MAIN terminal from the battery (with the negative still in) and very very slightly touch the battery post with it. If you can see a wee bit of spark on the battery post, then you have an electrical leakage somewhere. Best time would be in the evening when it starts getting dark. I had a similar problem 2 years back and saved myself the cost of diodes and alternators. It was a main wire from the brake light touching body metal!!


Club Member
The diode pack in the alternator is very, very reliable. Like Fiji Nissan says, you can check to see if any current is being drawn from the battery. I would suggest using a multimeter to measure the current though. Make sure you don't start the car by mistake when doing it....
Hmm that's interesting... I've been getting those sparks all along... thanks guys, good tips there about the sparks and service lives of the diode packs.
To finish the story, got an auto spark to look at it in the end. Tracked the problem down to loose wiring coming off the positive side of the battery causing the battery to keep momentarily disconnecting. The guy thought this was causing alternator regs to blow.

Reconditioned alternator and much improved wiring later, she's hot to trot, running better and starting fine (with the battery connected overnight). So that's good then. :grinning:

Thanks for the advice on it folks.