Hello,
I have a 2008 F150 SuperCab 5.4L 4wd. Recently experiencing a charging issue. Went to start the truck last week; had low crank but she started after a few seconds. Drove short distance, turned truck off, ran into store and came out about ten minutes later. Went to start truck and got clicking. Attempted a few times with no luck. Had someone jump me. Truck started. Turned on headlights (dark out) and was about to put truck into gear and noticed the gauges looked good, then dumped dark (all showing off). Also had random dash lights turn on then off (ABS, Charging, O/D, SeatBelt). Truck was still on and the headlights appeared to be dimmer. Drove less than 200 feet or so and the lights went out. Then several feet later, truck was off (all power gone). Attempted to try to restart it and just got clicking. Parked truck after being towed and attempted to restart it with the same clicking. Checked charge on battery (less than 9 volts). Borrowed trickle charger from a buddy, recharged the battery. Reinstalled battery and watched voltage. Initially, alternator was working (reading around 14V with engine on and then tested again while the system was loaded [lights, radio, blower, etc] and got a reading around 13.5 V or so). Then all of a sudden volts dropped to 12. Pulled battery and alternator and had tested at Autozone. Both showed good. I then inspected cables and ran continuity tests through wiring from battery cables through alternator cable and voltage regulator cable with resistance at around .3-.1 ohms on both negative and positive sides. Also completed Voltage drop tests on both positive side and negative side and got around .1 or so volts-nothing significant. Pulled fuses linked with PCM and anything I could think would be associated with charging system and all were good.

Reconnected everything today and saw alternator was putting out around 14V for a while and even when loaded. Then all of a sudden volts dropped to 12.3 and decreased slowly. Hooked up OBDII reader to look for codes and nothing. Then had reader complete KOER test and received the following code-P0625. Then charging light came on (first time since this started). Everything I have been seeing points me in several different directions. I read about a PCM issue; the voltage regulator; the fusible links. I am currently stuck and looking for some direction.

If I need to take it to the Ford dealer, I will, but I would like to be able to narrow them down as best I can. I have read about several people buying up to four alternators, only to continue to have a similar problem keep coming back. Any help would be appreciated.

 

Replace your alternator.
I bought one from Ebay for $105 but worked fine for me.
I also rebuilt my original with Ebay's kit for spare.

 

Our trucks are very picky about Alternators... and you need one ... i would get a motorcraft replacement and be done with it..

 

I have the same issue as the OP, I have an alt coming today from Amazon. Like Hongster I'm gonna buy a rebuild kit so I can ave an extra alt in case the amazon one craps out.

 

So replace the alternator even though it was bench tested at Autozone and it was good? Is there a way I can test the altenator/voltage regulator myself (that I haven't already done) to confirm this before I go and replace it just to be sure there isn't something else causing my problem? I have read about too many people replacing alternators on these trucks just to find out there was something else that was going on. I just wajt to be sure so I don't start wasting money needlessly. Thanks in advance.

 

So had the alternator replaced with aarm reman by stealership. Voltage output showing 14. Shall see if this was the full problem. Hopefully-cost an arm and a leg as usual. BTW if anyone takes their vehicle to a dealer they charge around $143 just to do a full charging system check (battery and alternator). Ouch.