I find myself reaching out to this awesome community once again. I have a 1974.5 Datsun 260z (Oct 1974 build date).  Two weeks ago all was right with the world. I'd had a nice afternoon of driving the Z. I stopped to fill up the gas tank and when I started the car back up none of my gauges were working. Nothing but the speedometer (it's a mechanical connection). Fast forward to this Saturday an my battery alone will not start the car.  I get a jump start and try to make it home. It's night and I have my headlights on. By the time I make it approximately 10 miles to my home my headlights are barely visible. Here are my questions.

Do you think that the gauge issue is connected to the battery/alternator issue?

based on the photos below, do you think my alternator is the original (or a stock replacement) or has it been upgraded to a newer internal voltage regulator type alternator?

I have charged the battery and the car starts and runs fine for the short drive I had today. 

I'd appreciate your guidance on solving this issue. Thanks!

Looks like original Alternator.

Do you have voltage regulator hanging on the passenger side of engine room?

http://www.viczcar.com/forum/topic/11564-engine-bay-inspection-light-lenses-free/?p=137844

The Engine Electrical (EE) section of the factory service manual has procedures to check the voltage output of your alternator/regulator as well as other diagnostics. That is a good starting point.

I lost all my gauges when my alternator started "back charging" on my 1972.  That caused the fuse to blow as soon as I turned on the key so check for a blown fuse too but it sounds like the alternator needs replacing to me.

Seems like the internal regulator had gone bad on the alternator I had.  You could stop by an auto parts store and have them test it, quick and easy. 

Siteunseen, I failed to mention that i had checked the fuses on the passenger side floorboard area and they were all OK.  Is there another location I need to check as well?

Thanks!

Have you checked your fusible links? They are in the engine compartment. Things were moved around in the late 260Z, so I can't say for sure where they are located.

7 hours ago, tamo3 said:

Looks like original Alternator.

Do you have voltage regulator hanging on the passenger side of engine room?

http://www.viczcar.com/forum/topic/11564-engine-bay-inspection-light-lenses-free/?p=137844

It most likely is externally regulated. If the alternator was swapped for an internally regulated alternator, the battery would die more often from the fuel pump relay being energized all of the time. The coil for the fuel pump relay is wired between the alternator and regulator on the 260Z.

SteveJ, is the item I circled the coil for the fuel pump relay?

No, that is the condenser. It is a capacitor that reduces electrical noise. 

The fuel pump relay is in the passenger compartment, probably on the passenger side kick panel. Unfortunately I can't say for sure since you have a late 260Z. The wiring that goes to the fuel pump relay is hidden in the harness between the alternator and regulator. If memory serves, it is spliced into the yellow wire.

I went to AutoZone and had the alternator tested and the voltage regulator is bad. It appears that this may be a cheaper fix than I expected. Thanks for all y'alls help. 

 

wonder how they determined the VR was bad? The OE VR is a pretty simple devise, just a couple relays and points. If the alt is ok maybe a fuse link. An easy test for the alt detailed in the FSM consisting of supplying voltage to on of the term on the T connector on the alt.

Otis, I had the same charging problem with my '77 280 including the day I picked it up 40 years ago. Went through 3 oem voltage regulators over the years until I replaced it with a solid state unit from Advance Auto Parts. No problems since then. Easy replacement, relatively cheap. Good luck!

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