Well I purchased an 06 150 5.4, the used car dealer had replaced the alternator but the charging system message was still coming up, he said it would be taken care of, claims "we can't get it to come back on" yet it comes up often for us. I've researched dozens of threads regarding this issue. Some have said replace with only a "new" ford unit, been told probably can't find a new one given the model year, found a broken and corroded wire going from alternator to battery, repaired to no avail. Had alternator tested at local parts store and told not charging, yet dealer said his guy checked and it was! A little history according to carfax the battery and alternator were replaced at ford dealership jan 2015, and I've discovered that a "jumper wire" is running from the 3 wire plug on the alternator to the middle large plug going to what I believe is the PCM, on passenger side firewall. I'm considering having a Ford dealership run it through a diagnostic scan, if I do have a bad alternator maybe the dealer I bought from will replace if I have print out proving not charging. Anyone had and resolved this issue?

 

Not sure what Alt you have installed now...but, our trucks are very picky about Alt’s...you need a Motorcraft Alt. A decent re-man Motorcraft should work for you.. It’s a voltage Regulator thing.

 

You will not find a new one. I went through this. They only have remans including the dealers. I had to put 3 consecutive "motorcraft" alternators on before my battery light would go off. My 04 for some reason had a 130 amp alt on it according to the sticker but a vin search called for a 110 amp. It and my newer battery always tested good and seemed to be charging when I put my multimeter on it but my battery light would always come on after a minute or so. Truck always started but probably wasn't charging correctly. A whole other argument whether motorcraft remans have quality parts or not but stick with motorcraft and yes it has something to do with the voltage regulators. I think Rock Auto carries them but I stayed local and spent like $200 ish. I think Ford wanted around that with a pretty good warranty

 

Local Ford dealership ran scan, nothing, alternator charging. Wiggle test prompted them to suspect 3-wire plug off alternator, $237 labor and $63 for plug all seems well so far.No guarantees though just an expensive guess!! Will update if it reappears.

 

Could have gotten a new alternator for that