280z alternator issue-helping a stranded fellow Z guy

[IdahoKidd]

Hi guys,

I am trying to help a 16 year old with a charging problem via phone and texting and could use some help while I search for clues.

It is a 77 280z, all stock. The voltage meter apparently works but the red altenator charge light is on. The altenator has been tested and is producing 14.4 volts at the altenator, but no charge to the battery. The battery obviously goes dead in a relatively short time. As best I can determine (150 miles away) when the engine is reved, the charge light goes out.

Sorry for the sketchy info, it is all I have at this time. I sold my 280 and don't have one to go look at. It sounds like a fuseable link or some thing that is interupting the flow. Any help would be greatly appreciated!

Thanks,

Leonard

More: Alternator, Battery and voltage regulator are all new trying to fix the problem

Edited January 5, 2012 by IdahoKidd
additonal info

[black gold man]

Voltage regulator or diode are bad inside alt.

[IdahoKidd]

Voltage regulator and alternator are new (day old). He mentioned something about it not shutting off sometimes, which tells me diode too. Problem didn't go away with the new parts. Trying to determine is there is a fusable link inline somewhere that may be an issue.

thanks

[Zed Head]

The 14.4 volts he's measuring at the alternator should also show up as 14.4, minus the voltage drop along the way, at the thick white wire on the starter lug, which should be connected to the battery through the positive cable. That's where it ends up after it feeds the fusible links along the way through the wiring harness. Did he forget to connect the white wire at the starter?

He should see voltage at each of the fusible link terminals also. Has he measured there?

The charge light is controlled by the L wire, which comes though the VR plug and harness, if I remember right (it's one of the wires that is reconnected if you swap to an internally regulated alternator).

The charge light going out when he revs the engine seems to say that the L circuit is there though, since it's feeding back to the light. I would guess that the alternator is bad and is not getting, or properly using, the excitation current from the L wire.

More measurements at more points might show something.

Edit - found a mistake in the FSM. Deleted my post-comment.

Edited January 5, 2012 by Zed Head

[ckoepke]

I had just found out what the issues was. It was a very corroded fuseable link that was really fragile and brittle. Replaced it, and haven't had and issue with it for about a week or so.