1974 260z current drain

[Zed Head]

You need a simple but effective test.  The "click" is not it.  Looks like you know how to measure amps.  Set up your amps measurement and disconnect the two wire plug at the alternator like SteveJ said. 

No need to identify wire colors or look at diagrams.  Then you'll know if there is a short to ground through the F circuit of the VR.

Make sure the key is off.

On 11/21/2022 at 9:40 AM, Dolfinz said:

 I have a 2.5A drain on the battery without the ignition on. 

 

55 minutes ago, SteveJ said:

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.

disconnect the two wire connector at the alternator 

 

[SteveJ]

It's not a short to ground. The field wire should be dead with the ignition off. The VR controls the field wire.

[Zed Head]

The field wire is connected to ground.  The short is inside the VR.  The path is not as long as it's supposed to be.  With the key off.

We can argue semantics but the test is valid.  

[Dolfinz]

With the 2 pin connector disconnected the current draw is around 250mA

[SteveJ]

The 250 mA seems high, but you would have to do further testing to see if that's from your alternator.

[Dolfinz]

I disconnected the alternator completely and the current draw actually varies between 250 and 400mA.  Not sure why it would be fluctuating.  Seems like their might be something else responsible for a current draw as well?

[Zed Head]

W is connected to the battery through the fusible link.  Signs are pointing a short to ground inside the VR.  

If it was in my hand I would measure resistance from the W pin to the B pin on the VR, with it disconnected.  That would be where the path to ground is.

[Zed Head]

p.s. also measure from the VR case to W.  The case is used as ground according to one of the previous drawings.  They show the meter between yellow and the case.

[Dolfinz]

If I disconnect the VR, alternator is still disconnected,  I still have the fluctuating current draw

[Dolfinz]

If I disconnect either of the fusible links the current draw goes away

[Zed Head]

On 11/21/2022 at 9:40 AM, Dolfinz said:

 I decided to check for a current drain and sure enough I have a 2.5A drain on the battery without the ignition on.  I tried disconnecting the shunt and no drain.  I then disconnected the fusible links one at a time and no drain with either disconnected. 

 

On 11/22/2022 at 10:25 AM, Dolfinz said:

The voltage regulator is new.  I disconnected it and the current draw dropped to around .4A. 

I then disconnected the alternator with the voltage regulator connected and the current draw was still around 3A.  

 

2 hours ago, Dolfinz said:

If I disconnect the VR, alternator is still disconnected,  I still have the fluctuating current draw

Went back through your posts and see that it's not really clear when the draw occurs and/or how much.  And, my memory of a current draw I had was that even 0.3 amps will kill a battery after a day or two.

So, you have a draw with both the VR and alternator disconnected.  How big?  Fluctuating does not tell enough.  How many amps or milliamps?  Seems like you might have a short in the wiring and the short is to a wire that passes through the VR and/or alternator.

My wiring harness in the engine bay had some melty looking wires in it when I unwrapped it.  Something had shorted in the past and heated them up but they survived.

[Zed Head]

How are you measuring the draw?