CarConnection

did you swap out the gauges in the dash? the 280z voltmeter can cause a drain through feedback to the alternator.

Datsun350Z

iTrader: (7)

Yes, it has Full Autometer phantoms, but I can unplug the entire dash assembly and nothing changes, so I know its nothing in the gauges.

pdsq98gt

It sounds like you have a bad ground somewhere and it is causing a backfeed into your guages. Whatever has a bad ground is getting ground through that LED that is dim.

Datsun350Z

iTrader: (7)

If there was a bad ground linked to a gauge issue, then it would happen only when the key is turned on, because there is a constant 12V supply through the ignition powering the gauges.

It is only when I hook up the positive lead to the alternator that this drain starts happening. Everything that is grounded to the chassis has a backfeed into it after that, which would cause a feed into every light in the car, but the amount of power is so low that a very small LED is all it can make flicker.

pdsq98gt

How do you have your pcm and engine grounds ran? I would run a redundant ground from the block to the battery, chassis to the battery just to make sure that's not the problem. I know you don't think it's a ground problem, but I would almost put money on it.

Datsun350Z

iTrader: (7)

I have a ground from the battery to the block, the block to the chassis, and the PCM is grounded to the grounding bolt on the back of the block.

ryanvv355

iTrader: (17)

If the charging, starting and car circuits are all in parallel from battery +, I would think a bad ground draw would be evident regardless of the alternator being connected, unless power is back feeding through the exciter wire or case shorted to ground.

Datsun, do you know if the draw goes away with the car running and the alternator online? Is the alternator even producing current?

Datsun350Z

iTrader: (7)

Im 99% positive that the alternator is producing current while running, as I drove it back and forth to work for a few weeks.. and I just unplugged the neg terminal when I parked..

The drain could not be from the exciter wire being back-fed, because when I unplug it, the problem still occurs.

I still need to try taking the alternator off of the car and checking for the drain, and checking to see if the problem is still there while the car is running. I will try to do all of that tommorow

The stunningman

iTrader: (47)

Sounds like its time for a new alternator. Disconnect both hook-ups to the alternator. Then test for the short.

Datsun350Z

iTrader: (7)

Well, back at it again today with the new alternator..

I have left the battery hooked up for around a week or so and its held a great charge! No more short/drain symptoms...

BUT

I took it on around a 5-10 minute cruise and the thing would basically shut down every time I got on it hard.. I was definitely WTF'ing..

So I get to auto zone and get out and buy some ****, then I get in the car and try to start it, nothing. Battery is completely dead. So i got jumped and limped it home. Got out the voltmeter while it was still BARELY running.. and the battery was reading ~6 volts!! DANGIT!

I get the alternator tested later on after limping the car home after getting a jump.. Oreilly tested it and said that it was fine!! So I get home, reinstall the alternator, charge the battery, and look at the voltage with the car running.

The Voltage with the car running was ~ 12.48, revving the engine did NOT make a difference in the voltage, which it should have with a good working alternator..

So I took the alternator cable off of the battery, and tested it basically alone. With the engine running the alternator is putting out .9 volts... not 9! .9!

I also tested resistance from the alternator cable with it off of the battery, to a engine/chassis ground cable.. I had 168 ohms.. should there even be a readable ohm value here?



I know this is long guys, but im sure this would really help someone with a similar problem!!!


Cliff Notes -

New alternator
No more drain issues
Alt puts out only .9 volts
Voltage at battery when running is 12.43
Car will drain battery while driving
Alternator has been tested at oReilly and showed a pass.

ryanvv355

iTrader: (17)

Ok, first thought, not to insult your intelligence, but I know how things can get when your stressed under the hood. Was the multi-meter on the correct range? Is the alternator cable big enough to handle the current output of the alternator?

Datsun350Z

iTrader: (7)

Yea im positive everything was on the right setting.. which is why I would believe the .9 volt alt output as well, considering that the car drained the battery after driving it ~10 minutes or so, and the car would drain so much juice when I got on it really hard, that the computer would shut down and turn back on, hence the abrupt STOP in acceleration and no more pedal response for a few more seconds. Also now, the car will idle very erratically, randomly shooting the rpms up and down...

God this is driving me INSANE!