Chg and brake light

[Captain Obvious]

Haha!! Sounds like a plan!

I'd keep an eye out for weird behavior for a while too. I'm not really liking the timing of the failure of the VOLT bulb. Just too coincidental. Keep an eye on your voltmeter for a while.

[AZDatsun]

Ok problem not solved but I found out what triggers this symptom but no idea why it happens hear me out... if I have my car in gear and I am releasing the clutch without giving it gas so it kinda starts to stumble like it’s going to stall.. I hear the relay click and then the chg light and warning light came on.. gave it gas and push in the clutch and all the lights went off except the brake warning light.. try that process again and hear the relay and all lights turned off... and I did this process like 3 times in a row turning the lights off and on using the almost stall give it gas method... what in the world is that about. I can make this happen on demand when I want now by almost stalling the car.. and when I think about it when I was at the intersection I was in first with clutch in when I was letting the clutch out when the light turned green.. I am guessing it has something to do with the RPMs dropping when almost stalling so the alternator is not doing it’s thing...

 

 

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[Zed Head]

So you can make the brake light stay on by doing that?  If you turn the key off and start from scratch does the light stay on?  Or do you have to do the whole process over again?

Sounds like a stuck relay.  Letting the engine almost stall "unlocks" it and it gets stuck where it shouldn't be.  Since you know where it is you might try the old tap tap tap bang bang test.  Bring a tool and give it a few raps when the light stays on.

[AZDatsun]

I can make the brake and charge light go on by almost stalling it when letting out the clutch and when I give it gas with the clutch in I can make them go back off when the rpm gets above 1200 or so. Sometimes one light or the other will stay on until I repeat that process again but every time the rpms drop I hear the relay click and the lights come on. I did not try turning off the car and back on to see if that cleared the lights but I can try that tomorrow. Might take it down to get battery and alternator tested tomorrow

 

 

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[Captain Obvious]

Well most of that behavior is completely normal. The alternator output can (will) drop if the RPM's get too low. And if the alternator output drops far enough, the warning lights are supposed to come on. There are two things that concern me a little though, and that's why I was suggesting keeping an eye on things.

1) The alternator output might be dropping off at an RPM that's higher than normal which may be a sign that the alternator may be having some sort of internal problem. I don't know what the specs are, but on my car with an internally regulated alternator, my alternator output seems to be able to keep up easily at 700 RPM idle, even with the headlights and blower motor on. In other words, even with the headlights and blower motor on, I can let my RPMS drop to idle (700 RPM) and my warning lights don't come on. Might be a warning sign that yours do

2) The other thing that concerns me is the "latching" of either the VOLTS or BRAKE lights. Even if the alternator output does drop off at low RPM's, both those lights should go back out when you rev the engine. Every time. So if one or the other of those lights ever "latch" on, it might be another sign of impending doom for your current alternator.

Makes me wonder if your brushes are worn to a nub and are making intermittent contact. Or your internal regulator may be failing.

In my experience, things like this are warning signs that something is brewing. Might not be critical. Yet. But something's going on...

[AZDatsun]

My alternator is the rock auto ac delco reman. Probably just going to head to NAPA today they have their Napa power premium plus remain with limited lifetime warranty no harm in trying that out. If I get the same symptoms might be the relay


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[Zed Head]

You can watch the car's voltmeter to get another clue.  It will drop down to battery voltage or lower, from charging voltage, before the relay clicking starts.  You might find that while driving with some electrical things on, like blower motors, or AC, or sound, that you always drop to battery voltage at a stop.  That's not good.  Your brake lights draw might be enough to put too much load on the system, so you don't see it while testing in the garage.

The reman alternators are kind of notorious for low output at idle RPM.  Dim lights at idle, weak windshield wipers, and other problems are common with the Z's.  I ended up with a wrecking yard 280ZX alternator on my car that was better then the OReilly Auto Bosch reman.  

You said you got 13.45 charging, which is actually a bit low.  I got 14.3 with mine.  

[AZDatsun]

Alternator replaced going to test it all tomorrow including voltage readings but it started right up and sounded like a better idle but could just be my imagination. Too hot in the garage today in Phoenix


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[Captain Obvious]

Hope that's the end of it!

Send some of that heat our way please? We're running about 20 degrees below normal and I'm ready for some warmer weather. I'll be sure to send the heat back west to you before July so you don't miss out. 

[AZDatsun]

Ok results battery at 12.75 resting then 13.85 at idle still wish it was higher but more importantly the almost stall test succeeded, that was with all lights radio etc on. Also my radio has a blue light around it that glows that used to pulse with the music I thought that was a feature of the radio turns out of you have a good alternator it doesn’t pulse and the voltage gauge stays steady.


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[Zed Head]

I bumped up my idle RPM by about 100 and it made a difference.  Might get you an extra 1/2 volt at idle.

[Captain Obvious]

The results look promising but keep an eye on it for a while.

2 hours ago, AZDatsun said:

radio light used to pulse with the music I thought that was a feature

Haha!! Nice!  Just keep an eye on everything!