2005 F250 6.0, 215K miles, owned since new all maintenance preformed mostly on time and all the things that can go wrong did! Currently on extended RV trip. Short side of issue, Batt light intermittent-truck running check with multimeter- light on or off-13.8 volts at batteries. Later Batt light on more than off, checked batteries-12.0 volts after long drive time. AutoZone-test-batteries good-low-need to charge before test alt. Charged overnight-test alt-internal regulator failed-New not rebuilt alt-installed-charged batteries-light on after GPs off- alt output 0. Test new alt at AutoZone-internal regulator failed same as old alt-batteries 90% & 100%. Test old alt 7 times all pass don’t think it the alt. Miles later batteries low-charge overnight-start-drive 10 miles-oil 140 degrees-no Batt light-test volts at batteries with multimeter truck running-14.3 volts- go to turn truck off-Batt light on-test again at batteries 12.5 volts. Ohm test between Alt red wire and battery-good. Engine on-warm-no output from alt-engine off-key on-no voltage on green wire. Did not test other alt wire. Checked fuse 45-good. Do not see issue with oil temp wire. If I understand correctly-engine cold-GPs on-no power to alt-after engine oil warm-GP off-power to alt at green wire. Is this correct? Is the voltage to alt controlled by the GPM? If so, which wire can I test out of the GPM to see if it is providing voltage to the alt. If not, where does green wire get its voltage? Any suggestions appreciated. Thank you!