i know this is a problem common with most mid 70s GM cars and trucks, but my alt light stays on dimly all the time. my alternator is working just fine, and the battery is good. i am pretty sure it is a grounding problem, and have seen it in lots of GM vehicles from this time period, and i see my 77 has the same issue. problem is, i dont remember what the cause and the fix was for this. does anyone here know how to fix this?

signed......"i must be loosing it" :? :oops:

One blown diode in the diode trio inside the alternator.

hmmm....i thought there were 4 diodes. if a diode was out, wouldnt the alternator be malfunctioning, over or undercharging? i havent run a test on it yet with the meter, but it seems to be functioning as it should for the amount of driving i have done in it.

The diode bridge takes care of rectifing the AC to DC with 6 diodes (two for each phase). The trio has one for each phase and sends current to the regulator system. It is a little black piece that has three connections onto the bridge and one leg over to the regulator.

that makes sense. with one diode to the regulator, you could get a slight draw on the circut....enough to light up the idiot light. thanks. :thumbsup:

my light in a 79 elky stays on i replaced the alt and had the new one tested its doing the same as the original ! light is on all the time batt is charged good and voltage is good where is the resistor they show in the schematic located ?? could it be bad causing the light to stay on ??i have added some ground to body straps is there a specific location i should out one ???thanks