Ok so first off I have a 1977 280z. I am currently using an alternator from an oldsmobile cutless 1981. This is a 83amp alternator. Everything is mounted and wired correctly. As of recent I have been having the issue of charging. Now my charging light turns on with the engine off. I have checked the resistance in the yellow and black wire from the alternator to the battery and I read 40ohms. I believe spec is 35ohms. Now the factory volt meter is inaccurate. 14v charging looks like 16v (I have verified no over charging system charges at 14.7 when charging). Now heres where things get interesting I have seen the voltage drop when putting a load on the system lights, blower and even just brake lights. I have replaced the altinator a number of times thinking I have a bad or faulty internal regulator. and now the headlights will not turn on. From what I'm seeing in the wiring diagram I see one wire that comes from the voltage gauge and eventually ends at the headlight. Is it possible that all my problems are due to my voltage gauge?

 

Thanks for your help

Edited April 10, 20169 yr by Driftinrican

You have current following a wrong path.  The charge lamp shouldn't get power with the key off.  Check the circuit before the lamp and meter.  Sounds like your problem doesn't have anything to do with the alternator.