The Ford Barn

cas3 · 12-14-2025, 11:22 PM

Well, after Allens response, I'll try to help. It looks like the common 10 SI, that should be stamped on the case near the volts/amp rating. The white wire looped around to the power post makes it a one wire alt. The black wire will go to battery, but should be switched so it will not run the ignition off the alt after you turn off the key. Originally, that white wire went to the idiot light in the dash. Some folks wire it that way so you don't have to bring up RPM's to trigger it to start charging. There are a few different ways to wire the 10 SI, a google search will bring up diagrams.

No idea what the home made black box is, you'll have to trace the wires to figger out what they had in mind.

12-14-2025, 11:22 PM	#10
cas3 Senior Member Join Date: Jan 2011 Location: Beverly Kansas Posts: 5,557	Re: What type of alternator is this on my 40 Ford. Well, after Allens response, I'll try to help. It looks like the common 10 SI, that should be stamped on the case near the volts/amp rating. The white wire looped around to the power post makes it a one wire alt. The black wire will go to battery, but should be switched so it will not run the ignition off the alt after you turn off the key. Originally, that white wire went to the idiot light in the dash. Some folks wire it that way so you don't have to bring up RPM's to trigger it to start charging. There are a few different ways to wire the 10 SI, a google search will bring up diagrams. No idea what the home made black box is, you'll have to trace the wires to figger out what they had in mind.