I wrote a couple of weeks ago about charging my battery backwards and trying to install it. I ended up getting a new battery, but now the it is only charging at about8-10 amps. Could that be the alternator or is there something else that may have happened when I tried to install the battery?
I would pull your alternator and take it to O'Reillys or another auto parts store and have them bench test it.
It could be the VR (voltage regulator) on the back of the alternator is bad...
PS: this is when you might want to swap to a 3g if you have a 2g alternator... VR's are only $20-$40 but if you drive your truck tons, the 3G's do a better job. Not sure when ford put 3G's into F250's but you can tell easily enough 2G's have external fans and 3G's don't.
I seem to recall that you accidently charged your battery backwards (so that it had reverse polarity) and then connected it to your vehicle.
This usually damages one or more of the rectifier diodes in the alternator, which would explain your low charging rate. In addition, it can also cause a constant battery drain of a few amps (depending upon which diode in the rectifier goes out).
I agree with the above poster - this would be an excellent time for a 3G alternator upgrade. They are readily available (check the 1990s Tauruses) at self-service junkyards for under $30. I just got mine a couple of months ago but haven't installed it yet.
IMO those parts store alternator testers are worthless, I have had seen known bad alternators test good on them. My suggestion is to at least replace the alt with a rebuild that way you get a new regulator and rectifier.. which are both internal, I bet that will fix your charging problem. But before doing that test the fusable link to see if it's still intact.
OR combine both ideas... get a cheap JY 3G and a rebuild kit online and DIY the alternator rebuild yourself. Probably only cost $60-$80 total and you'd have a upgrade with good components installed. Unless you have a reliable rebuilder intown I would NOT buy a parts store rebuild unless they have a life time warrenty. Too many of the "rebuilds" you get from the chain parts stores are put together hasitly with cheap chineese or mexico parts... You can get quality rebuild parts online and do the rebuild yourself on a 3g and have the same money invested and an upgrade to your charging system to boot...