Fun with voltmeter

[Wstepler]

'77 280 with the 7127 GM alternator (internally regulated) with aftermarket stereo and fusible link upgrade I have a few issues. The main symptom is not charging. Besides for the battery not charging the other symptom I've ever seen is with the voltmeter and interior electronics. When car is off tbe voltmeter reads 0 volts. When the car is off all interior accessories also do not work. Hazards, radio (doesn't save presets,clock, cd track,etc), horn, dome light, dash lights (with headlights on)...) I turn the car on and nothing happens unless I rev the engine above 2700rpm. At this point the interior comes alive Horn, lights, radio, etc all start to work. The battery does not charge (shows 11.8v and dropping slowly) but of course my voltmeter starts to work and shows 16v with the charge light on. Just to rule out a few things I had access to a new battery and Reman/New alternator that have already been replaced. I did a voltage drop test on the positive side (positive post to alternator) and reads well above .2volts more like 3.0v . I'm somewhat lost. I've had 2 z's luckily no electrical issues ever but with all these upgrades/changes I'm not even sure where to start.

WarStep

'78 "The learner" Silver 280z RIP- Rust

'76 "The Favorite Child" N42/F54 Persimmon Red 280z RIP- Garbage truck :mad:

'77 "New Toy" KH3 Silverstone 280z

[Wade Nelson]

Quit screwing around on Internet forums and take your car to an auto electric shop. People get paid good money to diagnose auto electric problems, and deservedly so, IMNSHO.

The range of possibilities includes:

A failed alternator

Miswired alternator

Bad wiring and/or connector to alternator (likely)

Bad main engine and/or body grounds

Bad B+ wiring to fuseblock, failed fuseblock, miswired fuseblock

Bad B+ to alternator connection

Bad ignition switch (likely)

Some combination of the above. It sounds to me like you have multiple overlapping problems.

[Zed Head]

It sounds like your battery is only connected to the starter and the EFI harness and the alternator is only connected to the fuse box and body harness. The battery starts the car and the alternator runs the body electrical when it starts charging. The alternator behavior is like a GM one-wire setup, which requires revving to get it to start charging.

The charge light probably comes on because the L wire is not connected because someone has set up the "simple" (primitive) one wire alternator. The voltmeter's in the Z cars are not known for accuracy so the 16 volts is kind of meaningless, you need to use a real voltmeter. But before you do that, you should fix your wiring, it sounds messed up. It could be as simple as connecting the white charge wire from the alternator to the starter terminal,where it will be able to charge the battery like it's supposed to. Or it could be a nightmare wiring mess from a PO.

[240260280z]

Check fuses and fusable links