Battery going flat

[Russ]

Hi all,

Ok this has been happening about 8 months now and I've finally gotten time to look at it

Basically if I leave the car alone for about three days it goes flat.

It never happened when I bought the car, so I don't believe it's the alarm.

Before I blew up my multimeter I think I saw a 200ma drain on the battery with the doors shut etc.

I've had the battery tested, seems ok, and if I jump start the car the alt charges it fine and we're good to go after a fairly short journey for another three days.

I believe it could be a diode in the alternator? When I get a new fuse for my multimeter I'll see if I can track down the drain, but would be nice to know the usual suspects or if there is a way to test my alternator myself.

Cheers

 

[Pete]

I had a stuck switch on the seat mechanism that resulted in a flat battery if left standing for a while? (A faint click can be heard occasionaly as the seat tries to continually tilt).

 

[murt]

Arm the alarm and unarm it, see how much it changes, and see if its running stupid amounts of ma, also opena nd shut the doors, you know, that kind of thing

 

[datty240Z]

Try taking fuses out 1 at a time and see which one eliminates the discharge. This was how I found a short in my headlight wiring.

 

[rhanagar]

Try taking fuses out 1 at a time and see which one eliminates the discharge. This was how I found a short in my headlight wiring.

Best method really. Had this on an old Mk.1 Astra. Turned out to be the boot light.

 

[Russ]

I will get on it tonight, good thinking. I meant to do that but for some stupid reason in my head I figured the car is electrically sound and must be the alternator

Will let you know the results, cheers guys!

 

[rhanagar]

If it was the altenator you would probably get a battery light when driving and less than 14 odd volts when running.

Good luck with the investigations.

 

[Russ]

Cheers rhanagar, just put battery on charge, soon as I've fixed my multimeter i'll be all over it Fingers crossed it's not my head unit as that changed between car being fine and having the problem, can't afford another! heh

 

[zpuppy]

hehe,,still on the alternator tack, if the diodes fail the alternator will work just fine ,,but when the vehicle is shut down it will allow discharge through the field windings killing the battery .The diodes act exactly like a one way valve in your plumbing system really , only allowing current to flow to the battery not from. The only reason im keeping to the alternator is that it is a common fault with the 300 (ive found anyway) and easy to check wif a tester
Saying all that Russ, the problem could easily be any of the above mentioned and I dare say the above mentioned have a heck of a lot more experience with the Z marque than I do

 

[Russ]

Well I kinda was thinking it'd be the alt, in that I'm not sure what else on the swb 32 can go wrong. All my door switches should be ok as the alarm works, and I don't think I have a boot light that I know of. Will find out and let you know!

Can I test an alternator myself?

 

[SKiddell]

if the diodes fail the alternator will work just fine

...the diodes (output and trio) are part of the rectification circuit (bridge*), alternators inherantly output AC (hence the term alternator) if the diode pack fails you could get un rectified ac and if the trio fails possibly 3 phase....which your electrical system definately wont like...voltage regulator (internal) should stop it but 40 volts of 3 phase will soon fry that.

Now if a pair or single diode go down (usually short rather than open, sometimes just "leaky") then the alternator may "appear" to be working fine but will under deliver (DC componant will be excessively "pulsing"), battery doesnt get fully charged tra la la la plus the battery can "leak" down through the faulty diode.

*Note
Diodes in a bridge configuration form a bridge rectifier, this is sometimes in a pack form and replaced as a single item, sometimes it is a formation of 4 or 6 individual diodes depending on AC source phasing

 

[zpuppy]

well put SKiddell ! much better explain than mine , for whatever reason i have had on 3 occasions had a "leaky" diode,,charges fine but kills the battery every couple days. As i said theres lots of you fellas out there that know more than I about this stuff

 

[Russ]

From a bit more research I believe I'll need a tool I don't own to test for a leaky diode, will get a clamp meter on it and start pulling fuses

 

[RobZ32]

You can test a diode with most meters continuity one way through but not the other. Finding the one to test might be more difficult there are quite a few in the z32 wiring.

 

[mario]

if you have the time, the easy way to check and see if its the alternator, is charge the battery up, disconnect the red cable that goes from the battery to alternator, make sure you tape the end, or put something over it so it doesnt short out on anything, connect the battery, and leave it standing for a few days, or as many days as its been going flat, then try starting it. if it starts up as it should do, then you have your answer. normally, a .01 - .02 (100 or 200ma) drain is either a relay, or interior light circuit. just a word of advice though, a standard multimeter is only normally ok for anything up to 20ma, anything above that will fry it. if there is a short on an alternator diode, then it will far excede 20ma, and blow your meter up.

 

[Russ]

Cheers Rob, hopefully I don't have to go that far

Nice thinking Mario, why not just disconnect the altenator and eliminate it from the potential problems, d'oh! My multimeter is good for 10amps, but the altenator will still toast that (probably how I blew the fuse last time ).

Cheers

 

[RobZ32]

Taking the alternator off to disconnect it as you would need to would be a right job. There are a few plugs at the back of the right side head light below the hicas pipes you could unplug it with a bit of blaspheming.

 

[Russ]

Sorry that's what I meant, disconnect the wiring if I can get to it, nothing on the 32 engine is easy to remove

Hoping though I pull some fuses and find a dodgy light 24 hrs time and I'll know

 

[Russ]

It was the bloody head unit. I've wired it in now on the ignition live instead of permanent live so at least when i'm not in the car it won't be draining it.

I guess there's a fault with it and it needs to visit the Alpine centre £££

 

[datty240Z]

Won't you loose all your presets now when turn the ign off? Same thing happened with my daughter's Micra and lad next doors Puma.