Voltage meter spikes intermittently.

[77Z]

Yeah, I'm referring to the gauge in the dash.  The new mechanical VR makes it read about 13vdc and the red light is on.  I interpret that to mean its accepting no input from the alternator and its running on battery.  When I put the old SS VR back, the gauge shows what normally is a good charging alternator at <16vdc and no light which has been normal for over 40 years.

The connectors match up just fine.  I'll need to check with S30Driver about opening up the factory sealed M-VR to check its contacts.

So, given I've got an external VR, both the SS-VR and the M-VR should function equally well? 

Just to freshen the original goal;  to resolve a needle-pegging spike indicated by the gauge in the dash intermittently. This is accompanied by apparent issues with the audio system.  A quick shutdown and a few restarts clear it up.  Cables are checked and all appears tight and un-corroded.

[SteveJ]

11 minutes ago, 77Z said:

Yeah, I'm referring to the gauge in the dash.  The new mechanical VR makes it read about 13vdc and the red light is on.  I interpret that to mean its accepting no input from the alternator and its running on battery.  When I put the old SS VR back, the gauge shows what normally is a good charging alternator at <16vdc and no light which has been normal for over 40 years.

The connectors match up just fine.  I'll need to check with S30Driver about opening up the factory sealed M-VR to check its contacts.

So, given I've got an external VR, both the SS-VR and the M-VR should function equally well? 

Just to freshen the original goal;  to resolve a needle-pegging spike indicated by the gauge in the dash intermittently. This is accompanied by apparent issues with the audio system.  A quick shutdown and a few restarts clear it up.  Cables are checked and all appears tight and un-corroded.

Don't trust the gauge in the dash for good diagnostics. Get a real voltmeter for that. The gauge is good for "Oh crap, there's a problem" kind of readings.

You know for sure there were issues with the old voltage regulator, just from the potting material being cracked. That could have allowed corrosion on the underside of the circuit board. 

Pro tip: You can use a sewing pin or a T-pin (office supply stores) to back-probe a connector like on the voltage regulator to see if it has the right signals. Let me know if you get a hand-held voltmeter, and I can walk you though taking measurements.

[Zed Head]

Since it's so easy to swap them, one thing you might do is to check the connections in the plugs carefully and make sure that they are fully seated.  Spray some contact cleaner, make sure the plug is fully inserted.  All signs say that it should work.  

[S30Driver]

@SteveJ   77z wants to remove the top of the regulator and inspect and possibly clean the contacts.   What do you think?

I agree, verifying the connector signals would be great, especially if a pin was swapped for the aftermarket regulator.

[SteveJ]

There shouldn't be any parts that fall out if the VR is in good condition.

However, it might be better to document the pin arrangements (wire colors) on both the engine harness and VR first. Something might jump out to us.

Basically it's like the alternator isn't receiving the field signal from the VR recently installed. I would have to dig into to the circuit again to postulate the causes.

What I would really like to see prior to tearing into things are some voltage measurements at the battery prior to starting and at 2500 RPM. 

[77Z]

Got a multi-meter and will measure if you can list what I'm measuring  The new M-VR is on the bench so I'll take a look inside and run some paper with cleaner through the contacts and also work over both connectors and report back.

[SteveJ]

It will be a while before I can compile a list for you. I have a car coming over today for me to work on.

Meanwhile please take photos of the VR with the cover off. Try to frame some of the photos where I can see the internals and the wires coming down to the connector.

[Zed Head]

2 hours ago, SteveJ said:

However, it might be better to document the pin arrangements (wire colors) on both the engine harness and VR first. Something might jump out to us.

I think the colors shown in the FSM are the body harness colors.  If anything was switched it would be there.

[SteveJ]

12 minutes ago, Zed Head said:

I think the colors shown in the FSM are the body harness colors.  If anything was switched it would be there.

Exactly. That's why I asked for pictures with the cover off and the wires.

[Zed Head]

I'd be willing to trust 77Z's vision.  W/R = White with red stripe, etc.  The only secret is that L = blue.

[77Z]

Viola!  The new VR works now!  I took it apart, violated the warranty that expired 44 years ago and moved all the contacts for freedom.  One of them was stuck.  See photo.  I unstuck it and problem solved.  The dashboard gauge reads ~14 and no charge light.  

However... following ZedHead's advice I checked the harness wires.  I need to do some cleaning to complete the check, but right off the bat I see that my body harness wires are different than EE348 (which is the relay end).  That W/R is NOT at the top on the car end.  I believe its Blue/white at the top.  The White/Red is 1 pin to the side.

Before I put it all back together nicely, I want to finish the wire checks and get some cleaner for the contacts.  Then, I'll monitor for the mystery spiking.

THANKS GUYS!  I've been into most everything on this Z over time, except the VR. So, its hard to imagine that the harness/pin were changed.  There's a possibility that my "Z-guy" in Benbrook, TX changed out the VR to solid state a few decades back (must have, since its not stock). But, I can't imagine pins were changed.

[Zed Head]

I have vague memories of the wiring diagram colors not matching the car, in past threads.  I think it ended up as just one of those things that is, reason unknown.

The wait for voltage spikes is on now...