1974 260z current drain

[Zed Head]

Didn't find a specific test but did find a drawing.  I think that "A" might be stamped in to the back of the alternator.  Set your meter to resistance and measure between the A terminal on the back of the alternator and the alternator body.  It should be infinite resistance.  OL.

[Zed Head]

It is.

[Zed Head]

If you measure low resistance from A to ground then your alternator is probably bad.

BUT.  It could also be the wiring.  Check resistance from the A terminal in the harness to ground with both the VR and the alternator unplugged.

No offense intended, but this is one of those cases showing why people should get familiar with how their meter works, when everything is working right.  This problem is really kind of a "measure...check, measure...check, measure" kind of problem.  Simple things to check to narrow the problem down to a certain area.  Many of us have a list in our heads and once the meter is in hand it's just check, check, check, fault.

You can even check resistance through the pins of the VR.  I was going to suggest to SteveJ that he do that before he sends out his unused VR.  Check resistance from the battery feed pins to ground.  If it's open there should be no draw caused by the VR.  If SteveJ was at your car he probably would have done this already.  The meter is your friend.

[Zed Head]

Here's the plug to the VR.  Not sure if it's the harness or the VR side though.  Nissan just kind of stuck it in there with few words attached.  They show the labelled plug but the test is done from the "yellow terminal".

 

 

[Zed Head]

Some of the stuff I wrote above is probably wrong for this specific case.  Because A is also usually connected to the battery positive post.  So if it was shorting through the alternator it would short even with the VR unplugged.  It's just one of those things to check overall.

So, in sum, it still kind of looks like a bad VR.  IF the wiring is not shorted to ground somewhere.

[Dolfinz]

I checked from A on the alternator to ground and there was no continuity with the VR plugged in and the wht/red wire disconnected.  I'm confused about the VR test.  Is this performed with the VR plugged in?  Am I checking for voltage from the yellow wire to ground?  What do you mean by 'You can even check resistance through the pins of the VR.'  Check resistance on which terminals?

In my previous post I was asking if the positive feed from the VR is then fed to all other wiring and the fuse box?  As Zed mentioned in his last post couldn't there be a short to ground in the wiring after the VR that is causing the drain?  Is there a way I can verify that this isn't the real issue and not the VR?

If we still conclude the VR is the issue then Stevej please PM me and we can arrange to get it shipped.

[SteveJ]

If the VR is bad, I would expect to see voltage to ground on the F terminal of the alternator all of the time when everything is connected. That is the white wire. If there is voltage to ground at the F terminal when everything is connected, then disconnect the two wire connector at the alternator and see if there is still voltage to ground at the F terminal. If there is not, there is your proof. 

[Dolfinz]

With everything connected there is no voltage to ground on the F terminal of the alternator.

[SteveJ]

Is it still drawing current from the battery?

[Dolfinz]

Belay my last, I forgot to hook up the battery.  With the battery connected there is 12vdc at the F terminal with everything connected.  If I remove the wht/blk wire the voltage is only on that wire and not the F terminal.

[SteveJ]

That makes sense. Like I was saying before, the voltage regulator is trying to excite the field of the alternator to produce voltage even when the car is off. The way it works is that when you are trying to raise the voltage of the alternator you inject current (This is your current draw.) into the field coil.

[Dolfinz]

So then the VR is bad?  I'm guessing then that it should click when it's plugged in thus removing any current to the alternator unless the key gets turned on causing the relay to change states?