I have been having this issue since i bought my 74 120y.

1.Problem is my dash alternator light stays on and brightness increases with revs
2. When measure with multimeter at alternator and battery i get 14.5volts when reving about 2000rpm and up so seems normal
3. When i keep reving it the voltage stays at 14.5v but at arpund 5000rpm my alternator shoots sparks every where
4. I have tried 3 alternators and 4 new and used voltage regulators nondifference
5.have changed the whole dash with wiring look as i thought its a short somewhere still same problem
6. When driving and rpm get high enough alt light get realy bright and blows fush
7. When i connect the external voltage regulator my rpms drop so inassume thats normal and charging

Know im out of ideas and i disconnect my regulator to drive and have to charge my battery everynight


Please shoot some ideas on what it could be as im out of ideas

Just one thing it was converted by previous owner to manual from auto but i have checked the wiring and cant find any issues

Thanks

Well at least it is charging. 14.5 v is on spec

Yer i just dont underatant the charge light and sparks flying from alternator

Nt sure if putting a internal regulated alternator would fix it

Nope, no reason to expect that would solve it.

What is causing it? The charge light is controlled by the regulator, but seeing ad you tried several different ones it seems the cause is not the regulator.

At first glance I'd say the wiring is messed up.

Here's the wiring diagram.

Can anyone think of a reason the light would stay on even with different alternators & regulators (and even as its charging)?




a12datto120y, with engine OFF key ON, does the alternator light come on? Does it ever go out?

I just checked and no the alt light does not come one when i turn the ignition on only when instart the engine

The only light that turns on when inturn the igntiion to on isnthe oil pressure light which turns off as normal once instart it
Thanks

Sounds like it is miswired. Any signs that the wiring harness has been cut and spliced?

it does sound like a wiring fault, what is the voltage at idle?

Hmm thats all i can think of aswell
I can rule put the wiring in the dash as i changed the whole lot so shuld make it easier to find

Is got cut and joint wires to bypass the neutral saftey switch as previous owner has done a manual conversion

Il take all the tape of the wire and expose it all to look for shorts and wrong wiring tommorow and update what i find

Thanks