s30kid Posted June 16, 2014 Share Posted June 16, 2014 So, I have a 1977 280z 2+2 and the voltage regulator went out. Causing my voltage gauge to turn off and only work with the engine running, not charging my battery and most likey sending voltage spikes through my car. Anyway I had an old internally regulated alternator lying around so I had it tested at pepboys and I swapped them using the wiring diagram from atlanticz. The voltage gauge still does not show anything, until I start the car. Then it shoots up and hovers around 16v. but the alternator is putting out 15 and the battery is at 12, but was slowly charging so I thought nothing of it. well today I had torn apart my interior trying to trace down a shorted wire in my running lights circuit and I had grounded out a wire accidentally but it made my voltage gauge work correctly. But when I accidentally shorted the batt terminal on the alternator it started doing the same thing again. No voltage on the gauge when key off, acc, on. Only with the engine running. So I had found the short in the wire to my running lights and I ran a jumper wire around the short but the lights don't work when the car is off,acc, on like they use to. The lights only work with the engine running, and then shut off when the engine is turned off. And also my headlights stopped working, but the fuses are not blown. Im not sure if its just because my battery wasnt being charged and had gone down to 11v when i tried to turn them on but they always worked before. I only had probems with the running lights blowing their fuse. On a side note I have removed the combo switch and I use individual switches for the running lights and headlights so the combo switch is not the culprit this time. Any ideas on whats going on in my car? It has been a real pain and I am tapped out on ideas. I tore the whole car apart. Nothing is grounding out. the fuses are all good. I did the maxi fuse box upgrade on the fusible links and all thoes fuses are okay. Im just lost now. I have had this car going on 7 years now. Im so frustrated I might consider selling it and buying another z and start fresh. (...maybe) Quote Link to comment Share on other sites More sharing options...
Six_Shooter Posted June 16, 2014 Share Posted June 16, 2014 It sounds like you need to take it to an automotive electrical repair specialist, or a Datsun specialist that likes to do electrical repairs. I don't even know where I'd start with this one in giving advice over the internet. I know where I'd start if I was doing the work, and I do enjoy electrical, it's what I specialize in. You have some odd functionality going on, the voltage gauge should work any time the key is on. I think your en devour to bypass a short you may connected a couple circuits together that cause the lights to only work while the engine is running, but I can't even think about how to re-create this. If the battery voltage and charge voltage at the alternator charge post don't match, you need to find to why. This is essentially a direct connection, though there may be a fuseable link for this on your car, and this along with corrosion might be causing a loss of voltage. Quote Link to comment Share on other sites More sharing options...
s30kid Posted June 16, 2014 Author Share Posted June 16, 2014 Can I run Batt on the alternator directly to the battery + terminal? Or would that cause issues Quote Link to comment Share on other sites More sharing options...
m1ghtymaxXx Posted June 16, 2014 Share Posted June 16, 2014 I had lower voltage at the battery than alternator on my 83 ZX. The culprit was rusty battery and alternator grounds. The same grounding issue also caused my fusible link box to catch fire, created severely RPM dependant voltage (low charge at idle, over charge at high RPM), and caused the demise of several alternators and batteries. Quote Link to comment Share on other sites More sharing options...
Six_Shooter Posted June 16, 2014 Share Posted June 16, 2014 Can I run Batt on the alternator directly to the battery + terminal? Or would that cause issues That's how I usually do my alternator upgrades. Quote Link to comment Share on other sites More sharing options...
NewZed Posted June 16, 2014 Share Posted June 16, 2014 The stock setup does essentially that but there's a fusible link in between. Otherwise you could short your battery through a bad alternator or an accidental ground at the B post. Quote Link to comment Share on other sites More sharing options...
s30kid Posted June 17, 2014 Author Share Posted June 17, 2014 Alright I fixed the alternator issue! I ran a wire from the Batt on the alternator straight to the + on the battery leaving the original connector still in place because it did not work right when I disconnected it. Then I ran the S on the T connector (yellow wire) to the batt terminal on the alternator so that it will have 12v constant, I cleaned the ground with sandpaper on the connector and the body of the alternator, and everyting works correctly! My volt gauge works, the alternator light works, my battery is getting 13-14v. I guess my only other question would be could I run a ground from the alt to the body for safe measure or would it be pointless? Other then that it works great so far. Now all I need to figure out is how to fix my Headlights.. Quote Link to comment Share on other sites More sharing options...
dexter72 Posted June 17, 2014 Share Posted June 17, 2014 If only your low beams are out, run a new ground wire to the headlight ground wire circuit, before it splits to ground both headlights. Check your headlight wiring diagram to see where to splice the ground to. I added the new ground wire at the harness, where it comes through the right front of the core support. I had to do this on my 74 260z, worked like a charm. Big Phil posted a video on Youtube also, showing the repair to his 280z. Quote Link to comment Share on other sites More sharing options...
LLave Posted June 17, 2014 Share Posted June 17, 2014 Its not a GM alternator is it? I one time forgot to install the field wire, drove to the gas station and the car would not start. Took me a little while to figure out what was missing. Quote Link to comment Share on other sites More sharing options...
EvilC Posted June 18, 2014 Share Posted June 18, 2014 I have an overcharging issue going on right now on my 260z. Swapped to an internally reg alternator 2 years ago. I will be looking at the grounds next week and trying to trace down my issue. I still have at ammeter in my car so it spikes at +60 at driving speeds. Glad you figured out your issue. Quote Link to comment Share on other sites More sharing options...
s30kid Posted June 19, 2014 Author Share Posted June 19, 2014 I did the ground fix about a year ago. The one that phill posted. I dont have low or high beams. Nothing. I have the wiring diagram and I highlighted the whole headlight circuit I just need to find the time to do it. I might tonight if im not too tired. And the alternator I used was from a 280zx. Quote Link to comment Share on other sites More sharing options...
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