I bit the bullet and made an account, I don't know if this is the right place to post this. I'm having charging issues currently, as of a week ago the car was running great. It's a 77' 280z, currently the battery isn't charging and my fuel gauge fuse blows in the first stage. I've replaced the Alternator from Autozone, changed the Voltage regulator from MSA, also the fusible links also from MSA but it's still not charging. The first video is me turning the car on it stays at 12v constantly and when I turn it on it dips a bit then back to 12v and my charge light stays on even throughout the drive, the picture of the fuse is the blown fuse and that happens usually after the first stage of the key turn, and its the only fuse thats burns, the new alternator has proper tension, I'm curious what the P is on the wiring. I've had the battery tested and everyplace says it's good it just dies. I'm stumped please help!!??

Edited May 18, 20195 yr by Rodomania

I bought a bad alternator from Advance and it blew the fuse that runs my gauges. Mine had an internal regulator though and that was what was bad. As soon as I cranked the car my gauges quit working. I'd take the alternator back snd have it tested. The new one they gave I had it tedted before i left their store, failed too. Make sure and have the replacement tested also, they get a bad batch of them I guess so Advance went across the street and got one from autozone that passed their test. Good luck.

Edited May 18, 20195 yr by siteunseen

They call it "backwards charging" btw.

Do you have a volt meter other than the one in your car. If you do attach it to the battery. You should have around 12.4 - 12.6. Start the car increase RPM to over 1500 and check the voltage. You should get 13.8 to 14.1.  If not it may be a bad alternator.

So, the fuse blows at the first key stage. I'm assuming that is accessories. The next stage is on and the last stage is start. If that's correct, you've got a short circuit in one of the switched accessory circuits. Which fuse is the one that blows?

2 hours ago, siteunseen said:

They call it "backwards charging" btw.

after my buddy and i gave this mk1 sprite back to the owner he started messing with the wiring (he wanted a push to start button  ) and managed to mess it up so bad that the battery inverted its polarity. not sure why he did not just leave it alone and drive it, it was perfect when we handed it off.

Edited May 18, 20195 yr by heyitsrama

I did a total rebuild and new starter plus alternator went along with all that. Turn the key and popped the fuse. After a back and fourth with some smarter guys than me I put the old alternator back on. Worked great.

Took the new rebuilt one back and it failed their testing. I still have the OE on my 240, brand new rebuild is a dust collector on my shelves of many new rebuilt parts. They suck imho. Luckily they'll work on my d21 pickup.

7 hours ago, Rodomania said:

 changed the Voltage regulator from MSA, the new alternator has proper tension, I'm curious what the P is on the wiring. I've had the battery tested and everyplace says it's good it just dies. I'm stumped please help!!??

 

 

I think that you might have an internally regulated alternator with an external regulator.  The "P" is only found on the internal reg alts, I believe.  It's some sort of tachometer for more advanced charge control systems, I think.

Change alternators of wire it up for an external regulator.  No real advantage, one over the other, for a 77.  They're both 60 amps.

Here's the back of a Remy 1982 280Zx internally regulated alternator, for comparison.  If you just bought the car it might already be wired for an internal alt. You didn't really say why you changed the alternator so your original problem might still be there after you get the right parts back in to it.

Welcome to the club!