Unknown Current Draw

[tiberis]

Hey Guys,

Got something to rattle your brains here... i'll give you the back story though it may be unrelated...

on monday morning i got my air con regassed, it seemed to work fine. drove car for 10mins, stopped it for 5, got back in and drove for 15 mins to uni and everything seemed fine, air con was working.

i was at work at uni for like 5 or 6 hours.

come back to my car and it wont start, battery is half dead (lights on dash come up and it clicks). so i get it jump started from a friend. i wait there idling for a bit. it all seems fine, then the engine revs drop a bit, the hicas light comes on, then the engine dies.

i jump it again but the same happens again. i then disconnect the relay for the air con (thinking it's something to do with that)

i manage to drive it 10 mins home, but after i turn it off, i can't start it again, battery is dead.

i then get my house mates car to charge my battery for 10 mins, start mine up drive to petrol station, fill up, it starts again so i drive around for another 15 mins on roe hwy (thinking it would help charge the batt having the higher revs). i get home, park car, then this morning battery is completely dead again.

now, here is the confusing part.... i measure the current draw using a charged battery, and it says ~3.5-4A and nothing is on, keys aren't even in the IGN barrel. so i start removing fuses to try and track what is eating the power... i have now removed every fuse i can find (engine bay, driver's kick panel, near battery in boot) and it's still drawing ~3.5-4A!!!!

so has anyone every heard of something like this? or know anything else i can check?

(for reference, car is a 93 R33 4 door with RB25DET, pretty much no mods (no fancy alarm or other circuits wired in)).

[lachlanw]

fog lights ? air con clutch ?

[MrStabby]

Hmm air con clutch *should* be run from a fused circuit - can you hear it engage/disengage as you turn the aircon on and off?

[tiberis]

fog lamps are turned off (and fuse is pulled)

air con is disabled (no fuse or relay) as it was leaking anyways.

i was thinking aircon clutch, but yeah, i don't hear it.

thanks for the ideas guys, but no dice

[tiberis]

ok, just for reference in case anybody else ends up searching for the same problem.... because i believe i have found it!

i started unplugging/ disconnecting things that connect to the main loom and use +ive... disconnected the starter motor, but that changed nothing.

but then as i took off the alternator, i saw sparks... once fully disconnected, current draw was 0.

so apparently my alternator is screwed... but i;ve not seen one die like this before. i will try taking it apart later and if i find more info i will post it here for future reference to others.

[MrStabby]

i was thinking aircon clutch, but yeah, i don't hear it.

Not hearing it is and indication it might be the problem, as it might mean its always on... try disconnecting it to see if the load disappears. Finding where to disconnect it might be tricky, you'll need to follow the wires. IIRC there's a plug but on mine it was near impossible to disconnect.

[tiberis]

well, i was plugging and unplugging the relay for the clutch... so it should have been clicking on and off... or when i was connecting and disconnecting the battery. with the engine off it's pretty easy to hear anyways.

but yes, the plug for it is on top of the compressor, so you need to reach under the power steering pump and fumble blindly for a bit

either way, going to source a working alternator and go from there.

[t_revz]

if the larger white wire in the alternator plug has ignition supply then the alternator will be excited. pull the small plug off and see if the current draw drops. if not then must be alternator but if it drops then there must be a ignition relay or something stuck and sending power there with key off

[tiberis]

right... well i noticed the spark from the lead which is bolted near the back, which i believe is output (ie, to the battery).

not sure about the alternator having power from somewhere else and being excited... i pulled out every fuse and relay in that car... ones in the boot, ones behind the kick panel and ones in the engine bay. i also undid all the plugs near the fuses in the boot (just in case) so the only place getting power was that connection point near the relays in the engine bay... so unless there is some other hidden relay somewhere else in the car...

hopefully i can get an alternator tomorrow and confirm that it was at fault... otherwise i will end up going insane trying to track this problem down.

[t_revz]

the large cable on the back of the alternator is for charging the battery but alternator has a small plug with 2 wires to turn alternator on/off and for warning light. i would try disconnecting plug and seeing if it stops current draw before getting another alternator. i would have thought ignition supply to alternator would have come from fuse panel but the cables are quite large so prob a relay or fusible link

[tiberis]

replaced alternator, haven't taken the car for a run yet, but it started ok and was running fine for like 5-10mins

it was also charging the battery which is a good sign.

just to note, there was a whining kind of noise which must have been from the alternator (i thought it was air related so i didn't think much of it) which i think one of the diodes in the rectifier have died hence the drawing current as it is now short circuiting through that diode.

will update with final result soon. am still thinking that the whole aircon involvement was coincidence.

[R.3.2.G.T.R]

was it the alternator in the end?

[tiberis]

Yep, turned out to be alternator had a dead diode which was making a constant current draw.

alternator would still charge if you gave it enough RPM interestingly enough, it just wasn't as efficient.

So, 1 new alternator later and car has been good since then (except for the battery being old and dying, but thats another story)