Dustink

I bought my first ford a couple weeks ago for a song with a high idle issue and charging issue. It's a 92 f150 4x4. 5.8 auto. Thanks to lurking on this site, I replaced the upper intake gasket and fixed the high idle problem. On to the alternator. The wiring had been cut and spliced so many times, I couldn't make heads or tails of it so again(thanks to this site) I decided to do a 3G conversion and make it a 1 wire application. Got a donor alternator, hooked the yellow to the cable lug and hooked the cable to the solenoid. 12.4 volts engine off. Fired it up and it reads 11.7 at the battery. 11.5 when headlights were turned on slowly dropping. So I figure I got a bad alternator. Took it to the parts store and it checks out fine on the bench. Actually 15.2 output. Put it back on and same result. Bought another one out of a known car and same result. How can they get power out of these things on the bench, but I can't on the vehicle? How much easier can 1 wire get? Checked all fuses, not that it should matter. Grounds are all good and every other electrical component works as it should. I am getting .02 out of the green wire if that matters. I'm scratching my head here, any advice?

Blackbuzzard

Is there an external voltage regulator? I have no idea.

Put the multimeter probes on the alternator terminals when spinning, or rig a system to do so on truck safely. See if it puts out like 14vdc unloaded.

Clearly yer not getting charging voltage to the battery.......follow all the wiring very closely back to battery.

check cable continuity

good luck.

jp360cj

What's the alternator's output directly off the alternator while on the truck?