lights going dim almost dead while driving

ok something weird going on that ive never ever seen happen before, in all these decades of owning having trucks and vehicles in general...


i was driving the '75 C20 last night and even though the ammeter was reading the same a s always, normal(just past center of the guage -slightly towards the charging side)all the lights in the truck were really super dim and barely lit up at all, inside and out of the truck.
all the lights got even more dim as i drove, until they were barely lit up at all anymore, within minutes... and so I barely made it back to here, with barely any lights left at all..

the battery voltage and etc all perfectly fine normal etc...
the battery is actually brand new, as of a few moths ago. cables and connections all clean dry tight, no starting or reserve voltage issues at all.

just all the headlamps and dome lamp and dash lights etc. all went super dim almost dead...

weirdest chit ever...



i have noticed that only the pass side headlamp has gone dim, in the past couple weeks or so,
both the headlamps are identical halogen sealed beams stock.
and the alternator is the stock '70s 10SI 63 amp alternator.

the whole truck is a bone stock factory original 350 powered original wiring everything, and nothing is hacked cut spliced modified anywhere at all.


what could be causing loss of ALL the interior and exterior lamps brightness, but truck otherwise is totally fine??

maybe the HL switch? dunno?

Bad ground someplace? Bad alt?

ended up that the brand new battery puked somehow, it dropped to 11.6 volts and wouldnt even move the starter motor or charge any farther, even though alt and etc is fine..

i dunno why the battery decided to just spontaneously suicide itself... i swapped it out with another one and its fine again now.


do still have a bad ground or something somewhere, with being that the RH headlamp is still dimmer than the other.. hmm..