I just finished up a 3 wire alternator conversion on my pick up. I've got a 55 second series Chevy truck with a 235. I installed an ACDelco 321-39 63amp internally regulated alternator.
I followed the instructions for the harness I got with the alternator. The battery lead wire coming from the alternator battery terminal connects to the horn relay batt terminal, light switch batt terminal, ignition switch batt terminal, and Ammeter. The exciter wire from the alternator is connected to one of the ignition switch acc plugs. It has a pig tail (they call it an ACC connection jumper) and is connected to the fuel gage power supply. The instructions that came with the harness say to connect it all this way.
It's wired up and everything seems ok but I am having the engine continue to run after turning the key off. I believe this is because of an exciter wire back feed issue that I've read about on the forum. I disconnected the exciter wire from the ACC connector, leaving everything else the same, and the truck turned off like it's supposed to. It seems like after the key is turned off, the coil is still being energized by the alternator for some reason through the exciter wire.
I think I'll need a diode at the exciter wire ignition switch connection. I've done some searching on the forum and saw some posts recommending this. I found a lot of Radio Shack part numbers for diodes but they are no longer in business.
Does anybody have good diode recommendation and vendor? Or maybe I don't need a diode because I've got it wired wrong? Maybe it's a faulty alternator? I'm stumped!
Oops, one mistake on the wiring set up, specifically the exciter plug and acc connection jumper.
The jumper is not plugged into the gas gage power supply, it is plugged into a pink wire that connects to the circuit board on the drivers side on the firewall almost directly behind the light switch.
Wish it did, still won't turn off with the key. I look like a mad man running to the front of the truck and pulling the coil wire to shut her down every time.
I had that issue on my truck. I put a small light in the line that is red when you turn the key on, start the engine and the alternator starts charging, the light goes out. When you turn the engine off it goes off.
Jaydee, I have a three wire Delco alternator on my '57. I ran the exciter wire to the ignition side of the resistor on the firewall. I soldered a diode from Radio Shack into the wire where it plugs into the alternator.
Radio Shack is still in business. Fewer stores, but still in business.
