Car: 1974 260Z S30
So today I started my Z and the cranking was incredibly slow, it took 20 seconds of very slow cranking and the car started. Then I drive it for a bit and It seems to be fine.
I went to O'Reilly's afterward and have them test my battery and alternator, the machine at O'Reilly says it's a bad alternator and battery. I'm worried that the alternator regulator is zapping the battery because on my ammeter I see rhythmic jumps on charging only when idle. When I turn on my headlights or start driving a little faster, the jumping goes away.
My alternator is the old style with external regulators and after cleaning The regulator a little bit, I started the engine again and the jumping is less but still exists. I seen on fourm that it is normal but I have my doubts. My fuel gauge recently went out as well which I have a suspicion that the regulator zapped it.
I'm quite confused to what is happening but I would like some pointers to what do you guys think is the best thing to do now. I can go back to O'Reilly's and have them check it again after I clean the grounds n contacts (The regulator insides look pretty clean but have extremely corroded screws so I gave that a clean, sanded some paint off my mounting point for better contact and cleaned up the screws), or I can replace the battery but I am worried that it's going to be zapped again. Or I can replace the alternator with an internal regulator version but I really don't have money for that currently.
TLDR: My ammeter is jumping and has been for a while (I think I always had it) when idling. My fuel gauge recently started freaking out, and today I had a weak starter due to the battery being bad and relatively new.
Please let me know what is the best way to proceed, thank lads!
VID_20250527_194359223.mp4
