Datsun350Z

iTrader: (7)

I have been chasing a short in my wiring system for quite a while, and I am having considerable trouble getting anywhere with it!

- Things I do know..
I have my positive cable from the alternator, ran straight to the battery+.. Whenever this cable is removed from the battery, the short STOPS completely. I can still have the + ran to the starter and to my main system power, and there is no short at all.

So I thought that I had isolated my problem to my alternator.. so I bought a new one today, and well, no el fixo. The short is still leaking to chassis, and is putting out around .2 volts..

I have the 12V "IGN ON" wire that you run to the plugin for the alternator hooked up with the 500 ohm resistor.. one question I had is if that wire has to be a constant 12V, even with the ignition off?

Anyone, help is GREATLY appreciated and honored..

JoeyGC5

iTrader: (24)

So you have an "electrical drain" not a "shorted" connection? hat/where are you measuring to get the 0.2vdc measurement?
The wire to the alt shold be 12vdc hot when the key is on

Datsun350Z

iTrader: (7)

Yes I have a constant drain, and it is to the chassis, basically I can go anywhere on the chassis and have .2V... you can also tell by the way my auto meter speedo's odometer LED is kinda half lit and flickering very slightly..

The 12V to the alt is on when the key is on..

I also have NOTHING connected to the alternator, besides the 12V "ign on" and the positive... and this is on a brand new unit. Replaced my old alt thinking it was the problem and nothing happened. I can tap the negative terminal off of the post and see very tiny sparks, showing that there is something leaking voltage somewhere..

And just a reminder, it is ONLY when I hook up the alternator, that this occurs.

ryanvv355

iTrader: (17)

Did the drain fluctuate at all between the 2 alternators. Was it .2v with both alternators?

Isolate the alternator from the battery, take an ohms reading between the alternator post and the a good ground. If you have continuity unplug the connector on the top of the alternator. Check continuity again, see if it goes away. You could have an ECM problem.

Or you could simply unplug the connector and check your frame again for the .2vdc.

Datsun350Z

iTrader: (7)

Good Idea, will do this after class tonight..

The drain did not differ between the new and old alternator.

Also, I did try unplugging the connector on top of the alternator, and the drain was still present. The drain does not differ with the 12V exciter wire being hot or not. The 12V ~500ohm exciter wire running to the alternator is ran through an Ignition "ON" 12V source, and is not ran through the PCM in any way, its totally isolated.

Datsun350Z

iTrader: (7)

Just tried it really quick, and I have 106.8 Ohms, from the Battery Negative post, to the Positive Lead on the alternator..

Also tried it from the positive terminal from the alternator, to a nearby known ground, that is hooked to the engine - chassis.. and I had ~168 ohms..

So there is definitely a drain somewhere? I just went through the ENTIRE wiring harness and rewired everything last week and the problem still exists.

ryanvv355

iTrader: (17)

I had this happen to me awhile back in my Olds, before the LS swap, I did a bunch of troubleshooting and isolated it down to the battery itself. Replaced the battery and it was gone. However, yours has a little more complicated of an issue.

Ok next thing i would do, isolate the alt case completely from the motor leaving the main wire connected, bascially lift the alt up and put a rag under it so it is not grounded against the engine. See if you still have the draw. Try with the little plug unplugged and plugged in.

I am interested to know what is causing your problem....

ryanvv355

iTrader: (17)

What about the charge indicator light circuit coming out of the alternator? Are you using it?

Datsun350Z

iTrader: (7)

Nope, the only thing I have is the 12V 500ohm "ignition on" wire running to the exciter wire connector, and the battery positive.

ragefear

iTrader: (1)

what about running a continuity test between the terminals on the battery. What else is connected to the battery? Is the starter connected to it or is that connected to the alt or what?

Did this do this from the beginning or is it something new that just started happening?

ryanvv355

iTrader: (17)

Do not shoot continuity through the battery, you could smoke your meter. The circuit needs to be isolated from power to check continuity.

Datsun350Z

iTrader: (7)

This has been a problem since I built the car..

I still need to try removing the alternator from the car, when I try it I will be sure to update on the outcome

JoeyGC5

iTrader: (24)

For whatever reason it would appear the stator in the alternator (positive lead to battery connection) is conducting when it shouldn't be. If you place a test light or ampmeter inline with the lead from alt to battery and the light is on with the car off, theres the problem. I ask this because your resitance readings would show a constant load where the shouldn't be. What alternator are you using in your swap?

Datsun350Z

iTrader: (7)

Just bought a brand new one for an LS1 camaro, which is on the car now. The problem remained.

Before I was using a LS1 vette alternator..

Just tested: Battery+ > ampmeter > alternator + lead..

Got a .653mA constant drain.. I really dont see why this is happening unless the alternator would for some reason be shorting against the block?

Anyone else? I dont think the same thing would happen on a brand new AND an old alternator.

ragefear

iTrader: (1)

how is it connected? battery > alt > starter > fuse block harness? could be any one of those.

switch out the battery if you don't wanna test it with the ohm meter. I didn't have a problem doing that with my craftsman meter when I had a constant drain.

Could it be something on the interior? stereo? lighting? gauge? etc?

When I had this similar problem I had wires that went to the fuel tank melt together, positive to negative. Took me a year to figure that out, cause who thinks about those wires?

What about the wiring to the tranny? Werth a look see.

ryanvv355

iTrader: (17)

I agree that the problem is most likely not in the alt IF like you said the drain amount was the same with both alternators.

You said you can disconnect the duty field wire and the draw is still there?

Good call ragefear, how is the system wired, do you have the alt going straight to the battery and the car powered from the battery? or the car powered from the alt?

Chris10an

iTrader: (1)

do you use a wiring harnes from a truck or a F body?

Datsun350Z

iTrader: (7)

I have a custom wiring harness.. not really from anything, kind of like a painless harness except cheaper..

The cable runs straight from the battery+, to the alternator..

I have another cable running from the battery + to the starter, so does anyone think the problem could be that I dont have it ran as follows -----

How its not wired...

Battery+ > alternator.
Battery+ > starter

How it should be wired... and how I DO NOT have it..

Battery+ > Alternator+ lead > starter

Does anyone think that this could be the issue? I know back when I was piecing stuff together, that for some reason this is the only way I could make my amount of cable work..

ryanvv355

iTrader: (17)

Everything should be in parallel. Battery + terminal should go into three branches, one to alt, one to starter and one to the car.

Datsun350Z

iTrader: (7)

It is ran in parallel right now, just with 1 cable/wire per starter/alt/car..

I really dont understand how the alternator can be pulling amps with everything off unless there was an issue in the stator/alternator as someone else said, it really does not make any sense!!

Is there any way that the alt should be grounded or something? Am I missing anything?