3 wire alternator issues

So I roughed in the wiring on a new junkyard 78 amp 12si delco alternator yesterday and fired it up, but it had a pretty weak charge output. With only the electric fan running, the battery started with 11.5 volts and slowly drops.

I ran the main battery wire to the pos. battery post, the dummy light/exciter (terminal 1) to the ignition post on the solenoid, and the number 2 terminal voltage sensing wire to the battery side of the solenoid.

Im thinking the issues could either be lack of solid ground due to recently painted alternator bracket, or a bad internal regulator.

Any ideas? The current wiring setup should work, right?

 

The I terminal is only hot during cranking and 7 volts running. Find a hot in run wire to feed the alternator.

Sent from my Liberty using Tapatalk

 

Hmm, I thought the battery terminal (the hot terminal from the battery to the solenoid) was always hot. Ok, Ill give a different hot a whirl.

Thanks for the idea 73cj5

 

No the I terminal on the solenoid where you said you have the alt term #1 going to is only hot during cranking of the engine. Like said, you have to have the alt term #1 hot while in the run condition. That is why you need the diode if you are not using the idiot lite.

 

Alright, did some re-routing and she works like a champ! Lights, electric fan, heater and wipers all on at the same time and charging right on 14.5 volts. I disconnected the alternator until I get a diode in line.